Universal e-Paper Name Badge

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I have been fascinated by e-Paper since the technology was announced long time ago now. Back in 2017 a few of us did a group buy and purchased some black and white and a tri-coloured black/white and red e-Paper displays. These worked with the Waveshare ESP8266 and ESP32 universal e-Paper controllers, but I have always wanted to have a go at making my own controller. Mine is based on the Waveshare ESP32 universal controller, but I have added on a LM75 i2C temperature sensor and BME280 i2C temperature, humidity and air pressure sensor for the first prototype.

The aim is to develop a universal e-Paper controller, but also act as a name badge/room temperature sensor. The first version is larger than I wanted, but it has a number of handy test points and a Li-ion battery charger/booster circuit based on the TP5400 IC. It's also made on a 2 layer PCB. While I checked all the ESP32 pins I had chosen, at the last minute, I changed the two LED GPIO pins to use some closer GPIO pins. Unfortunately the ones I chose where input only, and I needed them to be output capable, so I have had to add in some bodge wires to some spare GPIO pins. Here is the board being tested with a 2.13" e-Paper display:

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Lots of software to be written and tested, then the next version of the PCB will be designed up using a smaller 4 layer PCB layout.

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The Adelaide Makerspace hosted a show and tell evening as part of the National Science week. I was luckily enough to be able to attend and display some of my PCB I have recently created. This included the current version of the e-Paper Name Badge project. I am on the road, so I have some time for software development. I now have the i2C bus IC's working well, and I have figured out how to display different fonts on the display:

e-Paper_Display_sml.jpg (253.32 KiB) Viewed 2240 times

Next up is to fix a couple of PCB errors, and change the PCB from 2 layer to a 4 layer PCB. This will allow the PCB to be designed up quite a bit smaller. The next version will include a MPU-6050 accelerometer, so the ESP32 will know which way is up, and adjust the text display appropriately.

In the current (first) version of the PCB, I included some test points around the e-Paper circuitry, so I could monitor how it works. I was surprised to see that each e-Paper uses different voltages. I have seen up to +-22 being used to setup the display!

I included two temperature sensors 1) LM75; 2) BME280. The former costs (2021), around A$0.47 and can be purchased in a very small form factor. The later is in even a smaller form factor, however its currently very expensive at A$11.00ea, but it is much more accurate at +- 0.5 deg C vs +-2 deg C for the LM75!

This version included a CP2102 UART, to make it easier to program, however, I might move to a ESP32-C3, which includes a built in UART, therefore freeing up some space where I can place the accelerometer.

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Today I upload the next PCB revision design to JLCPCB to manufacture. This will fix a couple of wiring issues and will include a MPU-6050 accelerometer, so the board will be able to rotate the text depending on which way your mounting the unit. I am also trialling a ESP32-C3 MCU. This is being billed as a ESP8266 replacement. It doesn't have many GPIO pins, but it comes with a built in USB UART, so I can now connect the USB data pins directly to the ESP32-C3 MCU. This helps lower the board BOM costs, and lowers the PCB real estate needed for the project. I have lots of spare PCB space, but I wanted to have a go at using the new MCU.

The ESP32-C3 isn't available from LCSC yet, it's too new, but I have purchased a Dev board and two version 2 modules from Aliexpress. While these are only a sample version, I believe the mass produced version 3 modules will be released very soon, and I can just hot air off the old V2 modules and insert the new V3 versions when they arrive.

e-Paper-Display-Controller_V0.7.jpg (79.51 KiB) Viewed 2219 times

This PCB will be done in a Blue solder mask (but KiCAD is showing it above in Green).

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I received the version 0.7 blue PCB, but due to the BME280 and MPU-6050 being unobtanium just now because of the silicon shortage, I decided to spin out another version of the e-Paper Name Badge PCB. Version 0.8 will be centered on a ESP32-Pico MCU, as it has more available pins and can be programmed in either ESP-IDF, or Arduino. I would have liked to have used the new ESP-S2, but the Arduino code is still in Beta.

This means that I will have to upload my programs (or at least the initial program), via an external serial UART, as I don't want to give up a lot of PCB real estate for a CP2102 UART IC. I have taken the opportunity to make the PCB smaller and as I still had some space available, I added on a VL53L1CXV IR swipe/distance sensor and a relatively power hungry (56mA), SGP30 CO2 sensor. This sensor runs at 1.8V, so I had to add in a SOT-23 sized 3.3V to 1.8V LDO regulator and a set of i2C voltage level translators. I think I will only run this sensor when it's on USB power, as the datasheet says that ideally it should run for 20 minutes at a time.

As per above, I ditched the BME280, and the LM75 and replaced them with a BMP388 air pressure and SHTC3 temperature and humidity sensors. Should be interesting to see how they all operate together on one board. The MPU-6050 was replaced with a tiny and 30 times cheaper LIS2DH12TR accelerometer.

ePaper-Name-Badge_V0.8.jpg (92.24 KiB) Viewed 1791 times

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Well, somehow the Australian Postal system lost this and another PCB from JLCPCB during shipping. This was during C19 dark days here in WA, so fair enough. Since the loss, I have discovered two things about this PCB:

1) the WS2812 foot print was wrong
2) the MOSFET driving the e-Paper power was in backwards. It worked, but would not turn off power properly.

These have now all been fixed and PCB V0.8a has been uploaded for manufacture. I am still waiting for the outcome of the loss. That should be interesting so see if or what I get refunded. I note that in the last few days, JLCPCB prices for white soldermask has increased to A$16 and for Red, it's now A$25! Ouch! This board is being done in pretty Purple.