FASANI CORPORATION

Trying out Waveshare E-Paper ESP32 driver board

Martin Fasani
, ,
, , , ,

In my pursuit to make the CALE displays as small as possible but also to learn how different boards interact with Epaper I got last week an Waveshare E-Ink ESP32 driver board.

ESP32 Waveshare Epaper driver

Not all the boards need to use the default SPI GPIOs of the ESP32 and this was one of this cases. Opening the documentation, the first check was to see that Waveshare used this PINS:

#define PIN_SPI_SCK  13  // CLOCK ESP32 default 18
#define PIN_SPI_DIN  14  // MOSI ESP32 default: 23
#define PIN_SPI_CS   15
#define PIN_SPI_BUSY 25
#define PIN_SPI_RST  26
#define PIN_SPI_DC   27

So my first though was Ok nice but this won’t work per se using gxEPD library. Because this great library starts the SPI.begin() withouth parameters hence using ESP32 /ESP8266 default GPIOs for SPI communication. So what I did to test is very simple, I forked GxEPD:
https://github.com/martinberlin/GxEPD-config-spi.git

And updated this part of the library to use defines that can be injected using Platformio build_flags:

SPI.begin(CLK_GPIO,MISO,MOSI_GPIO,CS_GPIO);
Note that MISO is already defined in espressif32 Arduino framework.
So now we can inject the other 3 in platformio.ini and get the Waveshare example working:
build_flags =
  -DCLK_GPIO=13
  -DMOSI_GPIO=14
  -DCS_GPIO=15

If we want to test it with CALE we can also use the same defines to reference the EInk wiring in lib/Config/Config.h

// Waveshare ESP32 SPI
int8_t EINK_CS = 15;
int8_t EINK_BUSY = 25;
int8_t EINK_RST = 26;
int8_t EINK_DC = 27;
So it was not a lot of time to get it working with this simple modification. I find it great to inject defines using build_flags. It’s really straight-forward and in fact, if they are only simple defines, all configuration for a project could be done just in platformio.ini

The party breaker

So I was excited to get this working and avoid using this SPI adaptors that go between the ESP32 and the Epaper display…until I got the idea to connect it to my small 3.7 V Lipo that I use to test the ESP32’s with a Diode in between to lower 0.5 v. and found out how much it consumes in deepsleep:
That’s 13 mA per hour. Unless I’m missing something and there is something big that needs to be switched of before deepsleep this EPD driver will eat your battery and your kids for dinner.
So that was the low point of this test. If someone’s got a clue about this high consumption when sleeping please write something in the comments.
UPDATE: In the measurement below I forgot to put the diode in serie, so I was giving 3.8 v to the 3.3 pin. Don’t try it otherwise you may kill the ESP32.  Adding the diode it went down to 3.4 v and consumption of course went also down to 10 mA. But is still a lot for deepsleep. In good ESP32 boards like TinyPICO and others, deepsleep consumption is as low as 0.08 mA.
Video proof: