2.2 spi tft lcd teensy 3.6 hookup price

The 7-pin display modules do not need "just" SPI, but also CS (Chip Select), D/C (Data or Command), Reset, and optionally a PWM pin for controlling the backlight. As KurtE mentioned, this should work in theory, but the problem is existing library support. The CS pins need to be separate, but all can share the D/C and Reset pins (although you cannot then reset just one display; you can only reset them all if you need to). There is always the risk that the display modules don"t like sharing their lines among so many modules -- for example, if there are too many pull-up/down resistors in the lines, or even if the modules don"t like their D/C pins toggled when their CS is not selected.

The existing ST7735 libraries I looked at do not use a canvas, but send the pixel data resulting from drawing commands via SPI. Assuming 16-bit RGB color, each 128�128 frame needs 32768 bytes; 128�160 needs 40960 bytes. With a full canvas, it would be much easier to support the eight SPI displays, because then the SPI transfers could use DMA. If the library is the only one using that SPI bus, you could avoid the CS pin restrictions by reserving the hardware CS pin (i.e., keep it unused), and let the SPI library think it is using hardware CS pins, too.

There is at least one seller on eBay with RGB TFT display modules (of various sizes) that support I2c. These have some sort of microcontroller on board, and you can set different I2C addresses for each module, so you should be able to control several of these on the same I2C bus (without the I2C multiplexer). Instead of pixel data, you send the drawing or writing commands as text to the desired module, so no library per se is needed. They also cost about three or four times as much as the above 7-pin display modules.

There are up to 1.3" single-color OLED displays using the SSD1306 controller. I have the white ones, and I like them quite a bit. Make sure you look at the four-pin ones. In the yellow/blue models, the pixels near the top are yellow, and the rest are blue, on a black background. So, each pixel is always the same color if lit: monochrome. The larger ones (0.96" and 1.3") are 128�64, the smaller (0.91") are 128�32.

Use eight identical I2C displays, and an I2C multiplexer like Adafruit sells (or a cheap eBay clone). You only need minimal changes to the Adafruit SSD1306 library, to fully support the I2C multiplexer. This is because the library only communicates with the display at init and display times. At init time, all displays need to be initialized (a new constructor function, that takes the heights of the up to eight displays into account, and drops the splash). A new variant of the .display() method takes an additional parameter, to choose the display to be updated with the current canvas; you can even update the same canvas to multiple displays. You can also add helpers so that the canvas is easy to load from a 1024- or 512-byte (128�64 or 128�32 bit) raw binary file on a microSD card (say, using Paul"s SD library), in case you want to display nice pre-drawn icons, and optionally add text/lines/bars on top. Drawing/writing text to the canvas is done using Adafruit GFX library. There is only one canvas, but you can send it to any display or displays. (You can obviously also keep the icons in Flash, but there isn"t that much room there.)

I could probably provide the changes, porting it to the i2c_t3 library (using DMA for the i2c transfers), but I don"t yet have a multiplexer to test the code, and my newest Teensy is a 3.2. The changes are really simple.

*Pin 13 is the standard SCK signal, but also is hooked up to the Teensy"s on-board LED, so the board will flash its LED whenever it writes to the TeensyView. Pin 14 does not appear to support SCK on the Teensy 4.0 or 4.1

*Pin 15 is the standard RESET pin, but also the only available pin for GPT capture. The GPT isn"t even supported in Arduino/Teensyduino by default, but is there if you do lower-level register-level programming. My project needed that as the input for a GPS PPS, so I had to use the alternate pin 2, which works fine (plain GPIO).

The Prototyping System for Teensy 4.1 provides a flexible setup for working with the Teensy 4.1 microcontroller, the most powerful Arduino compatible microcontroller available today.

The baseboard provides the core features required in many setups including power input handling, logic level shifting, touch screen LCD for user interface and access to common buses and interfaces such as Ethernet, USB Host, CAN bus, RS485 bus, Serial TTL, I2C, level shifted I2C, SPI, level shifted SPI, WiFi and Bluetooth.

A Fully Stuffed version that comes with everything installed and includes all the accessories needed to basically just plug and go.  The ultimate in instant gratification.  Just add the Teensy 4.1 of your choice from the list down below to complete a fully functioning setup.

Add your choice of Teensy 4.1 from the memory configuration options below and the system will be fully assembled with the example software preloaded.  Just apply power and the system will come up and run the example code.  Plug in the earbuds to hear the audio.

The Teensy 4.1 Fully Loaded for Prototyping System have all the headers installed to properly mate up with the connectors on the baseboard.  VUSB trace is cut and a Schottky diode installed to properly isolate power.

If you already have a Teensy 4.1 that you want to use with this baseboard, it is fairly easy to adapt to it with nominal thru-hole soldering skills.  There are instructions toward the bottom of this page.

The area next to the Teensy 4.1 is designed to provide flexibility for working with various adapters for adding functionality to the system.  We offer a number of options below and it is possible to design your own.

The area next to the Teensy 4.1 is footprinted to accept 2 of the standard size Teensy adapters such as the Audio Rev D adapter for easily working with them.

Because of the power of the Teensy 4.1, it is very popular for use with audio projects because it is fast enough to synthesize music on the fly and the PJRC team provides excellent tools like the PJRC Audio System Design Tool for working with their audio module.  We have a version with pins preinstalled so it will plug into the baseboard.  It also comes with a microphone installed.  One comes installed in the Fully Stuffed version along with a 32GB SD card preloaded with sample WAV files.

The PT8211 is a low cost 16-bit stereo Digital-to-Analog (DAC) with line level output.  It is supported by the PJRC Audio System Design Tool which makes it easy to use with the Teensy 4.1.  We offer a version that is fully assembled with male header pins to make it plug-n-play with the baseboard.  It is also available in kit form on the product page.

The PJRC team that created Teensy also put together a very nice workshop for learning about audio processing using Teensy since Teensy has the horsepower to synthesize audio on the fly.  They also created a powerful Teensy Audio Library and Audio System Design Tool.

We have created this adapter to provide the user controls for going through the workshop and have modified the original workshop and programs as needed to work with this baseboard in our Audio Tutorial and Workshop.  The board is shortened to less than full width to provide clearance to also mount the Teensy 4.x Audio Adapter at the same time.  Standoffs provide mechanical support.

If you have an interest in learning how to use audio with Teensy or just want to explore more of what the Teensy can do, going through the audio workshop is very informative.  This board can also be used to provide a couple general purpose potentiometer and pushbutton inputs.

The same adapter area is also footprinted to accept a larger 4″ x 2.5″ adapter with access to all of the Teensy 4.1 pins available along the two edges of the PCB.

This adapter mounts a 400 tie-point high quality solderless breadboard for building temporary breadboard circuits.  The female headers on either end of the breadboard provide access to all of the Teensy 4.1 pins.  This allows circuits to be built, the whole baseboard assembly with solderless breadboard to be moved around and then the breadboard subassembly can be removed intact and replaced without having to reconnect anything.  Great for bouncing between several projects.

We have created an adapter that makes it very easy to work with a string of addressable LEDs.  Just plug in the LED strip and a 5V power source.  The adapter also includes the functionality of the popular Teensy Octo2811 Adapter for larger arrays in a physical format that works better with this baseboard.  This allows up to 8 channels of addressable LEDs using CAT cable

The Teensy 4.1 socket brings all I/O out from the bottom of the Teensy 4.1.  The socket also has a row of male headers for easily connecting logic analyzer or O’scope probes or for jumping pins over to a solderless breadboard or making temporary connections such as patching in the high-speed logic level converters.

We offer our Teensy 4.1 Fully Loaded for Prototyping System line of Teensy 4.1 products that are configured for use with this board and similar baseboard setups that bring the I/O down from the bottom of the Teensy 4.1.  They include the following changes from the standard Teensy 4.1:

A female 2×3 2mm header is mounted at the Ethernet connector location on the bottom side of the Teensy 4.1 which mates with an extended reach male header on the baseboard and connects the Teensy 4.1 to the MagJack on the baseboard.

Male 5-pin headers are mounted to the bottom side of the Teensy 4.1 to bring down the USB Host lines to connect to the on-board Host USB connector.  VBat connects to a CR2032 battery holder and On/Off and Program connect to buttons on the baseboard.

By separating the VUSB and VIN power inputs and placing a Schottky diode between them, this allows the Teensy 4.1 to be powered from both the USB cable and VIN input at the same time if the VIN power source also has a diode installed.  It also allows the modified Teensy 4.1 to be powered on the bench from the USB cable without being placed into a baseboard which can be handy at times.

When used with a 3rd party baseboard, it removes the need to solder a diode onto the bottom of the Teensy 4.1.  When used with our Prototyping System for Teensy 4.1 baseboard, the Schottky diode on the Teensy 4.1 is in parallel with another one on the baseboard, so is redundant.

This 5V VIN power provides power to the Teensy 5V VIN input, the ESP32-S 5V input and the LCD display which all have their own built-in 3.3V regulators.

The VIN power also feeds a 3.3V regulator that powers the 3V power rail on the board to take the load off the Teensy 4.1.  This arrangement also ensures that 3.3V is available no matter how the board is powered to avoid the possible issue of driving logic signals into an unpowered IC.

The Teensy 4.1 onboard 3.3V regulator output is not used on the baseboard, but the power is available on the T3V pins of the Teensy 4.1.  If these pins are used, be sure not to connect the T3V pins to the 3V or other powered rail or damage could result.  The same is true for the 3V3 pin of the ESP32-S.

If USB power is also connected to the Teensy 4.1 along with DC input power, the board contains the necessary Schottky diodes to separate the USB power from the VIN power as long as the VUSB/VIN trace is cut on the bottom of the Teensy 4.1 as is done on the Teensy 4.1 with offer for use with this baseboard.

The entire Teensy 4.1 footprint is brought out to the proto adapter area.  The outer 24-pin female headers support connecting to all of the Teensy 4.1 I/O pins and can fit a 4.0″ x 2.5″ adapter .  The inner 14-pin headers support inserting up to two of the standard PJRC 14-pin adapter boards like the popular Teensy 4.x Rev D Audio Adapter.

The only electrical differences is that the SPI Clk pin 13 and MOSI pin 11 lines to the adapter area have 56Ω series resistors to minimize signal reflections.  A second set of resistors feed these same signals to the LCD.  The 3V pins in the adapter area power are supplied from the baseboard 3.3V regulator and not the Teensy 4.1.  0.1uF bypass caps are connected to each of the power pins in this area.

The board supports either a 2.8″ or 3.2″ 320×240 color touchscreen LCD with the ILI9341 display controller.  This is the best supported display for the Teensy 4.1 and readily available from ProtoSupplies.com and PJRC.  The 3.2″ version comes with the Fully Stuffed option.

The onboard SD card slot on these displays generally don’t work without modification and the Teensy has an SD card slot, so they are not usually worth messing with.  The 4 SD pin locations on the right side of the display are there for mechanical support.  This allows a 4-pin male header to be soldered to the display and plugged into the female header.  The two sets of female header are provided because the 3.2″ display has a slightly wider footprint than the 2.8″ display.

The Teensy 4.1 Serial1 on pins D0 and D1 connects to the ESP32-S Serial 2 on pins 28 and 27 to provide communications between the two microcontrollers.

The ESP32-S can be used as a co-processor to the Teensy 4.1 to offload all WiFi or Bluetooth work.  The ESP32-S is much better suited for that type of work than the Teensy 4.1.  It can also be used to offload other processing work such as to act as a dedicated sensor monitor and motor controller for instance.

The other pins on the ESP32-S are unallocated, so can be repurposed as desired.  A row of adjacent male header pins is provided to make jumping over to a breadboard or the Teensy 4.1 easy, such as if you want to work with SPI instead of serial communications between the two microcontrollers.

Two jumpers allow the Teensy 4.1 Serial 1 signals on pins 1 and 0 (1-RX, 0-TX) to be disconnected from the ESP32-S if it is desired to free up pins D0 and D1 on the Teensy or if an alternate communication scheme such as SPI is being used with the ESP32.

The board has a MagJack for making wired Ethernet connections.  Teensy 4.1 has all the circuitry built-in for connecting to Ethernet and the two just need to be physically connected.

Note:  Due to Ethernet PHY chip shortages and price increases, some Teensy 4.1 on the market are now being built without this chip and do not have Ethernet capability.  All of the Teensy 4.1 we sell for this system have the PHY chip and full Ethernet capability, but if you plan to source or have already sourced a Teensy 4.1 from somewhere else for use with this board, keep that in mind if you plan to use Ethernet.

The baseboard has a extended length 2×3 2mm spacing male header to pickup the Ethernet connections from the bottom of the Teensy 4.1 that has a mating female header installed.

There is also a 2×3 2mm male header next to the MagJack that allows a Teensy 4.1 with a male Ethernet header already installed in the normal position to connect to the MagJack using an IDC cable like is supplied with the Teensy 4.1 Ethernet kit.

The USB Host is a 2nd USB port that allows you to connect USB devices to the Teensy 4.1.  It is fully independent of the main USB device port, so USB devices can communicate simultaneously with Teensy while Teensy communicates with a computer via the USB device port.  The USB Host port operates at up to 480Mbit/sec.  Use the

For providing power to the USB connector, there is a jumper USB 5V to select between using the standard switched USB 5V power from the Teensy 4.1 T4.1 or using the external VIN 5V unswitched power VIN which can be handy for powering higher current applications without having to resort to a powered hub.

The Teensy 4.1CAN3 bus on pins D30, D31 is connected to an SN65HVD230, 231 or 232 CAN bus transceiver.  These parts are all equivalent parts in this circuit and selected based on availability.

The receive output of the transceiver on D30 has a jumper J8 that can be used to disable this input into the Teensy 4.1 if the pin is to be used for other purposes.

RS485 is a long-line serial communication bus that allows multiple devices to connect to the same serial bus over long distances of up to 1200 meters.  The underlying protocol is standard TTL level RS232 but with differential transceivers used to extend to long distances and support multiple device drops.  Speeds of up to 2.5Mbit/sec are possible.  Handy for device control of one or more devices over longer distances or in electrically noisy environments such as industrial control.

The receive output of the transceiver on D34 has a jumper J7 which can be used to disable this input into the Teensy 4.1 if the pin is to be used for other purposes.

In addition, a 5V level shifted version of both buses is also provided using the standard MOSFET setup and 2.2K pull-up resistors that will work for most applications.  5V and ground is provided for the level shifted versions.

The SPI bus is also routed to the adapter area of the board.  CLK and MOSI each have two 56 ohm series resistors with the output of one branch going to the breakout header and LCD display and the second branch going to the adapter area to minimize reflections on the bus.

Serial7 on pins D28and D29 is brought out to a 4-pin header on the back edge of the board along with with 3.3V and ground for easy hookup to a serial device.

A CR2032 coin cell batter holder is located under the LCD display.  This connects to the VBat on the Teensy 4.1 for providing battery backup capability.

The On/Off button when pressed and held for 4 seconds turns off the Teensy 4.1 3.3V onboard regulator, thus shutting the Teensy down.  Pressing the button again for 0.5 seconds while off will turn the  3.3V back on and reboot the processor.  Note that this On/Off button has no affect on the baseboard 5V or 3.3V power.  It only affects the 3.3V regulator on the Teensy module itself.

Since designing basic PCBs through quick-turn houses is fairly easy these days, this feature allows users to design and build application specific circuits without having to deal with all the details of building a complete system which can be fairly daunting.  This can also be handy for designing and testing subsystems while prototyping a design before committing to a complete ground up design.  The adapter footprint is simply a 3.6″ wide Teensy 4.1 pinout as shown below.

A custom PCB height greater than 2.5″ can also be used if the overhang is on the front edge of the board or can also be on the back side if the LCD is not being used.

If you already have a Teensy 4.1 that you want to use with this baseboard, it is fairly easy to adapt to it with nominal thru-hole soldering skills and a sharp knife by following the directions below.

If you ordered the Fully Stuffed version and want to verify the basic setup works before modifying your Teensy 4.1, the unmodified Teensy can be installed in the socket and connected to a USB cable to download the example software.  Power for the baseboard will also come from the USB cable.  The ESP32-S will already be programmed so the setup should run as soon as the Teensy 4.1 has been programmed. Please Note:  It is important to not also apply power through the DC input on the baseboard until the Teensy 4.1 has been modified as follows or damage could result.

Cut the trace between the pads on the bottom of the Teensy 4.1 to isolate the USB power from VIN power.  Use a sharp X-acto knife or box knife with a new blade.  Angle the blade at about a 45 degree angle and press straight into the trace on one side.  Don’t use a sawing motion as you are just cutting through soft copper.  Move the blade to the other side of the trace and repeat the process to remove a small wedge of the trace.  A magnifier definitely makes this process easier if you have access to one.  A properly cut trace is shown at the bottom.  If you have a ohm meter, use it to verify the cut was successful by measuring across the pads.  You should not measure a dead short.

Install a female 2×3 2mm header on top of the tall 2×3 2mm male header if you Teensy does not already have a male header in that location.  Push it just slightly onto the male header, so you can align the pins with holes in the Teensy 4.1 first as you install the Teensy 4.1.

Install the Teensy 4.1 into its socket making sure that the pins of the headers you just installed all line up with the holes in the Teensy 4.1 and protrude through.  It doesn’t hurt to give a light tug on a couple of the 2×3 2mm female header pins to make sure it is seated firmly up against the bottom of the Teensy 4.1.

If there is a male Ethernet header already installed on the top of the Teensy 4.1, an IDC cable like provided with the Teensy 4.1 Ethernet kit can be used to mate with the male 2×3 2mm header next to the MagJack if you are planning to use that feature.

The setup described in this section illustrates the basic usage of some of the core parts of the system and provides a starting point for anyone just getting started with the Teensy 4.1 ecosystem.  It assumes that at least an LCD is installed and also looks to see if an ESP32-S and Teensy 4.x Rev D Audio adapter board with SD card are also installed to enable additional functionality.

If you ordered the Fully Stuffed version along with a Teensy 4.1, it will already be loaded with this software and will run as soon as power is applied.  If you ordered a Fully Stuffed version without the Teensy 4.1, you will just need to load the software into the Teensy 4.1 as everything else will be setup.

The programs are not overly clever on the programming to make them easier to follow (and because I am not overly clever at programming) and pull heavily from various sample programs.  The communications between the Teensy 4.1 and ESP32-S in particular are handled in a very simplistic fashion by passing simple text strings.

Checks to see if any of the PSRAM or Flash memory chips have been installed and reports that info out the serial port.  If you ordered a system with the Teensy 4.1 already installed, this also provides a way to verify that you received the correct version without having to pry the Teensy 4.1 out of its socket.

Configures the LCD display and touch screen and paints a couple of buttons on the screen.  One for playing audio and one for scanning for WiFi networks.

If a scan is requested, it sends the command ‘S’ for scan to the ESP32-S and then looks for a response back with the found networks.  The found networks are then listed on the LCD.

If the ESP32-S is installed and you have two USB cables, you can open two instances of the IDE with one connected to the Teensy 4.1 and one connected to the ESP32-S for downloading the programs and Serial Monitor windows can be opened on both to see what is going on.  This makes it easy to make program changes to either processor and download new code without messing with cables.  To open 2 separate instances of the IDE, they both need to be launched by clicking on the application icon.

Their are nine 0.138″ diameter holes which can accept up to 3.5mm or #6 screws unevenly spaced around the board.  The board ships with nine M3 8mm long nylon threaded standoffs and M3 6mm screws to provide mechanical support and electrical isolation when working with it on the bench.

Anyone working with the Teensy 4.1 should checkout the PJRC forum as it has exceptional technical support provided by a talented user base including Paul Stoffregen, the creator of the Teensy product line.

New Defines: DYNAMIC_BLADE_DIMMING, DYNAMIC_BLADE_LENGTH, DYNAMIC_CLASH_THRESHOLD, SAVE_BLADE_DIMMING, SAVE_CLASH_THRESHOLD, INCLUDE_SSD1306, FILTER_CUTOFF_FREQUENCY, FILTER_ORDER, NO_REPEAT_RANDOM, FEMALE_TALKIE_VOICE, DISABLE_BASIC_PARSER_STYLES and ENABLE_ALL_EDIT_OPTIONS

Make a config file. Usually, this will be tweaked and re-uploaded many times, but the best way to get started is to go to the Proffieboard V2, Proffieboard or TeensySaber V3 page and use the configuration generator. Go to the config/ directory, make a copy of one of the .h files, then rename the copy to "mysaber_config.h" (or whatever you like), then open up the file in an editor (like notepad) and remove all the lines, then cut-n-paste the stuff from the config generator instead and save it.

If you have a problem, you can contact me on The Rebel Armory or the fx-sabers forum, but there is also lots of online informtation about arduinos and teensys, so some googling probably won"t hurt.

The number - When playing a sound, TeensySaber will generally pick one of them randomly. The numbers can either be on the form 1,2,3,4,5,6,7,8,9,10,11, etc. or 01, 02, 03, etc. or 001, 002, 003, etc. The number sequence must be consistent and without any gaps. It"s also possible to omit the number completely. For looping sounds, TeensySaber will randomly pick one of the numbered files each time it starts over, so it"s possible to create a more interesting hum by having "hum.wav", "hum1.waw", "hum2.wav" etc. Note that since we"re using an ancient file system, the length of the name and number must not total more than 8 characters. (So you can only have 11 poweron sounds: poweron.wav, poweron0.wav, poweron1.wav....poweron9.wav)

4.9 - Font search paths, IR, SPI LED, Layers, presets.ini cleanup on programming, lightning block, melt, responsive styles, lots of new styles and effects.

5.9 - MICOM, initial Teensy4 support, RFID, I2S, S/PDIF, WS2811 speedups, FromHumFileStyle, EffectSeqence, CircularSectionF, MarbleF, SliceF, Saw, PullDownButton, SubBladeWIthStride

I"m still waiting for the last few components to arrive before I can build the controller, however one thing I wanted to do first is test my chosen LCD with the Teensy microcontroller. I"ve never used a TFT LCD with Arduino or Teensy before, so I first wanted to make sure that I could get the desired functionality and performance out of the LCD.

The LCD I am using is a 2.4" 320x240 TFT LCD with a ILI9341 controller chip which appears to be based off of an Adafruit design, which can be used with a Teensy-optimised Adafruit_ILI9341 library for better performance.

I decided to use the Teensy-optimised Adafruit_ILI9341 library over the standard Adafruit_ILI9341 library due to the demonstrated increased frame rate and performance of the former. I downloaded the library from the Github page and followed the provided instructions to install it into the Arduino software.

After a quick online search I couldn"t find any decent tutorials on using the LCD"s Arduino library to draw shapes (which is mostly what I want the LCD to do), however after dissecting the example sketches that come with the library it became quite clear how to do it. The best source to find out what functionality is provided is the library"s main header file, which shows all the functions that library provides such as drawRect, fillRect, fillCircle, and many more.

To test the LCD and Arduino library I decided to attempt to create a simple Teensy sketch that draws eight sliders on the LCD that each change their value from a MIDI CC message received over USB-MIDI - something that the final controller software will need to do.

Below is the code I created to do this. See the comments in the code to see how it works. The exact MIDI CC numbers I am using in this test code match the default CCs that the KORG nanoKONTROL MIDI controller sends from it"s sliders (see the below example video). If you would like to upload this to a Teensy yourself, you"ll need to set the "USB Type" to "MIDI" in the tools menu.

Below is an example video of the above code running on a Teensy 3.6, using a KORG nanoKONTROL USB-MIDI controller as the MIDI input device, with MIDI messages being routed from the nanoKONTROL to the Teensy using my MacBook running the MIDI Patchbay software.

The Teensy is a breadboard-friendly development board with a large number of features in a small package. Each Teensy 3.6 comes pre-flashed with a bootloader allowing to program it through the onboard USB connection; there is no need for an external programmer.

Users can program the Teensy working with their favorite program editor using C, or they can install the Teensyduino add-on for the Arduino IDE and develop Arduino sketches.

This lovely little display breakout is the best way to add a small, colorful and bright display to any project. Since the display uses 4-wire SPI to communicate and has its own pixel-addressable frame buffer, it can be used with every kind of microcontroller. Even a very small one with low memory and few pins available!

The 1.44" display has 128x128 color pixels. Unlike the low cost "Nokia 6110" and similar LCD displays, which are CSTN type and thus have poor color and slow refresh, this display is a true TFT! The TFT driver (ST7735R) can display full 16-bit color using our library code.

The breakout has the TFT display soldered on (it uses a delicate flex-circuit connector) as well as a ultra-low-dropout 3.3V regulator and a 3/5V level shifter so you can use it with 3.3V or 5V power and logic. We also had a little space so we placed a microSD card holder so you can easily load full color bitmaps from a FAT16/FAT32 formatted microSD card. The microSD card is not included, but you can pick one up here.

It is estimated that every year, 372,000 people around the world die due to drowning, and drowning is one of the top 10 unintentional causes of death [1]. As stated by the “National Drowning Report” published by Royal Life Saving Australia, there was a significant 20% increase in the number of drownings from 2020 to 2021 [2]. Many factors could lie behind drownings, including pre-existing medical conditions such as cardiac complications and drug or substance abuse [3,4,5,6]. However, the most common drowning causes are an inability to swim and panic in the water. In addition, unattended and unsupervised children comprise a substantial portion of the victims [7].

Based on previous research, drowning detection systems can be categorized into two major classifications: sensor-based and image processing systems. The former uses sensors such as pressure, heartbeat, motion, and depth, and the latter applies multiple algorithms to detect drowning through capturing images from live videos. Shehata et al. [8] compared different drowning detection methods by assessing the accuracy levels, complexity, and costs involved for the mentioned systems. In terms of cost and complexity, sensor-based devices are categorized in low to moderate classifications, whereas image processing systems are considered complex and expensive [8]. They often require drones to cover a wide area involving safety complications and practical challenges such as charging batteries for the drones. The accuracy is the only aspect where image processing techniques outperform sensor-based systems [8]. However, this is not the case when a drowning occurs underwater where the swimmers are not visible in murky water. There have been increasing attempts on developing sensory systems in the form of wearable devices to detect drowning. Chaudhari et al. [9] developed a device in which the heart rate is monitored and compared to a given threshold value and then transmitted using a radio with a range of 5–6 m [9]. The entire system can be attached to the swimmer’s head or hand, allowing easy mobility [9]. John et al. [10] proposed another module-based systems consisting of a heart rate pressure sensor. Recently, there has been a significant progress on developing sensitive sensors with small fingerprints which has potential for using in drowning detection systems [11,12,13,14,15,16,17]. For the transmitter side, the wristband design consists of a microcontroller together with a heart rate sensor, with two pre-defined thresholds for heart rate readings, i.e., high and low. Similarly, to the previous two-module designs, if a heart rate reading above the threshold values is recorded, an alert is sent to the receiver. A three-module system to detect drowning is presented by Ramdhan et al. [18]. The system is split into monitoring, access point, and drowning detection segments. The drowning detection module comprises a microcontroller with a pulse sensor to measure the heartbeat. The method proposed in [19] utilizes three sensors: an oxygen saturation level sensor, a respiration monitoring sensor, and a water sensor. These sensors are used for measuring parameters such as blood oxygen saturation levels, respiratory movements, and the submersion of a person’s body underwater, respectively, processed by a controller.

The LPS33HW can communicate via both I2C and SPI (Serial Peripheral Interface) methods of communication. Since soldering on such a small-scale pressure sensor is very difficult, the Adafruit LPS33HW breakout board was chosen for this project. The Adafruit LPS33HW consists of the LPS33HW sensor mounted on a breakout board and is small and compact. It has the option of connection via Qwiic cables and can register and display pressure readings with an accuracy of ±0.1% hPa. The highest possible pressure reading is equivalent to a 12.8 m depth of water, but the sensor is able to withstand pressure values up to 20 times the given measurement range. This feature is also useful to our proposed system, as it allows the system to apply to extreme depths of water bodies. The operating voltage of this sensor is compatible with that of the oximeter at 3.3 V. The sensor dimensions are 25.7 mm × 17.7 mm × 4.6 mm, and it is connected to a microcontroller using I2C communication.

The microcontroller implemented in this paper was ESP32 Thing (SparkFun Electronics, Boulder, CO, USA). This board operates on a 3.0–3.6 V voltage range and can be powered by a micro-USB port and a lithium battery. It also has an integrated Wi-Fi transceiver suitable for IoT (Internet of Things). The board dimensions are 59 mm × 25 mm, suitable for prototyping. It can also be replaced by smaller compatible devices when required.

The device employed a pulse oximeter and heart rate sensor, a pressure sensor, an accelerometer, and an OLED display. The pulse width of the OLED display can be changed in the program over a the range of 69–411 µs which allows the algorithm to optimize SpO2 and HR accuracies and power consumption based on various usage. Furthermore, the operating voltage of the sensor was 3.3 V. As a result, the power usage of the heart rate monitor was as low as <1 mW. The Adafruit LPS35HW pressure sensor could be used for either the operating voltage of 3 V or 5 V. The operating voltage of the accelerometer was 3.3–5 V, and its operating current was 8–10 µA in the low-power and low-noise mode) and 0.12 mA in the high-performance mode. The operating voltage range of the ESP32 Thing was 2.2–3.6 V, and its operating current was 150 mA when the Wi-Fi signal was active. The operating voltage of the OLED display was 3.3 V, and the maximum operating current was 100 µA. A 1100 mAh LiPo battery supplied the power of the waterproof portable device.

1. World Health Organization Drowning. [(accessed on 28 August 2021)]. Available online: https://www.who.int/news-room/fact-sheets/detail/drowning

2. Royal Life Saving Society Royal life Saving National Drowning Report; Royal Life Saving Society—Australia. 2020. [(accessed on 28 August 2021)]. Available online: https://www.royallifesaving.com.au/

4. Pajunen T., Vuori E., Vincenzi F.F., Lillsunde P., Smith G., Lunetta P. Unintentional drowning: Role of medicinal drugs and alcohol. BMC Public Health.2017;17:1–10. doi: 10.1186/s12889-017-4306-8. PubMed] [CrossRef]

7. Evans J., Javaid A.A., Scarrott E., Bamber A.R., Morgan J. Fifteen-minute consultation: Drowning in children. Arch. Dis. Child.-Educ. Pract.2021;106:88–93. doi: 10.1136/archdischild-2020-318823. [PubMed] [CrossRef]

8. Shehata A.M., Mohamed E.M., Salem K.L., Mohamed A.M., Salam M.A., Gamil M.M. A Survey of Drowning Detection Techniques; Proceedings of the 2021 International Mobile, Intelligent, and Ubiquitous Computing Conference (MIUCC); Cairo, Egypt. 26–27 May 2021; pp. 286–290.

12. Asadnia M., Kottapalli A.G.P., Haghighi R., Cloitre A., Alvarado P.V., Miao J., Triantafyllou M. MEMS sensors for assessing flow-related control of an underwater biomimetic robotic stingray. Bioinspir. Biomim.2015;10:036008. doi: 10.1088/1748-3190/10/3/036008. [PubMed] [CrossRef]

13. Dusek J., Kottapalli A., Woo M., Asadnia M., Miao J., Lang J., Triantafyllou M. Development and testing of bio-inspired microelectromechanical pressure sensor arrays for increased situational awareness for marine vehicles. Smart Mater. Struct.2012;22:014002. doi: 10.1088/0964-1726/22/1/014002. [CrossRef]

15. Kottapalli A.G.P., Asadnia M., Miao J., Triantafyllou M. Soft polymer membrane micro-sensor arrays inspired by the mechanosensory lateral line on the blind cavefish. J. Intell. Mater. Syst. Struct.2015;26:38–46. doi: 10.1177/1045389X14521702. [CrossRef]

16. Moshizi S.A., Azadi S., Belford A., Razmjou A., Wu S., Han Z.J., Asadnia M. Development of an ultra-sensitive and flexible piezoresistive flow sensor using vertical graphene nanosheets. Nano-Micro Lett.2020;12:109. doi: 10.1007/s40820-020-00446-w. PubMed] [CrossRef]

18. MS M.R., Ali M., Ali S., Kamaludin M. An Early Drowning Detection System for Internet of Things (IoT) Applications. Telkomnika.2018;16:1870–1876. doi: 10.12928/telkomnika.v16i4.9046. [CrossRef]

19. Kulkarni A., Lakhani K., Lokhande S. A sensor based low cost drowning detection system for human life safety; Proceedings of the 2016 5th International Conference on Reliability, Infocom Technologies and Optimization (Trends and Future Directions)(ICRITO); Noida, India. 7–9 September 2016; pp. 301–306.

20. Ramani J.G., Gayathri J., Aswanth R., Gunasekaran M. Automatic prevention of drowning by inflatable wrist band system; Proceedings of the 2019 5th International Conference on Advanced Computing & Communication Systems (ICACCS); Coimbatore, India. 15–16 March 2019; pp. 346–349.

21. Girela-Lopez E., Beltran-Aroca C.M., Dye A., Gill J.R. Epidemiology and autopsy findings of 500 drowning deaths. Forensic Sci. Int.2022;330:111137. doi: 10.1016/j.forsciint.2021.111137. [PubMed] [CrossRef]

26. Puspitasari A.J., Famella D., Ridwan M.S., Khoiri M. Design of low-flow oxygen monitor and control system for respiration and SpO2 rates optimization; Proceedings of the Journal of Physics: Conference Series; Yogyakarta, Indonesia. 6–7 September 2019; p. 012042.

28. Brianna M. 8 Truths about Drowning and ‘Dry Drowning’ Revealed. [(accessed on 28 August 2021)]. Available online: https://www.hackensackmeridianhealth.org/HealthU/2019/07/09/8-truths-about-drowning-and-dry-drowning-revealed/

30. Sparkfun Sparkfun Pulse Oximeter and Heart Rate Monitor Hookup Guide. [(accessed on 28 August 2021)]. Available online: https://learn.sparkfun.com/tutorials/sparkfun-pulse-oximeter-and-heart-rate-monitor-hookup-guide/all

NOTE: If the Teensy has more than one SPI buss. And the IO pins are all on a different SPI buss then that buss will be used. (i.e. you can use SPI1 or SPI2). With this, on a board such as a T4 or T3.5 or T3.6 you can potentially have three displays all on different SPI busses and using the Async updates you can have all three of them updating their display at the same time.

The teensy 4.x, 3.6 and 3.5 have a lot more memory than previous Teensy processors, so on these boards, we borrowed some ideas from the ILI9341_t3DMA library and added code to be able to use a logical Frame Buffer.