This e-Paper display uses SPI to receive image data. Since the display is SPI, it was easy to add two more SPI devices to share the bus - an SPI SRAM chip and SPI-driven SD card holder. There's quite a few pins and a variety of possible combinations for control depending on your needs
- 3-5V / Vin - this is the power pin, connect to 3-5VDC - it has reverse polarity protection but try to wire it right!
- 3.3V out - this is the 3.3V output from the onboard regulator, you can 'borrow' about 100mA if you need to power some other 3.3V logic devices
- GND - this is the power and signal ground pin
- ENAble - This pin is all the way on the right. It is connected to the enable pin on the onboard regulator that powers everything. If you want to really have the lowest possible power draw, pull this pin low! Note that if you do so you will cut power to the eInk display but also the SPI RAM (thus erasing it) and the SD card (which means you'll have to re-initialize it when you re-power
- SCK - this is the SPI clock input pin, required for e-Ink, SRAM and SD card
- MISO - this is the SPI Microcontroller In Serial Out pin, its used for the SD card and SRAM. It isn't used for the e-Ink display which is write-only, however you'll likely be using the SRAM to buffer the display so connect this one too!
- MOSI - this is the SPI Microcontroller Out Serial In pin, it is used to send data from the microcontroller to the SD card, SRAM and e-Ink display
- ECS - this is the E-Ink Chip Select, required for controlling the display
- D/C - this is the e-Ink Data/Command pin, required for controlling the display
- SRCS - this is the SRAM Chip Select, required for communicating with the onboard RAM chip.
- SDCS - this is the SD card Chip Select, required for communicating with the onboard SD card holder. You can leave this disconnected if you aren't going to access SD cards
- RST - this is the E-Ink ReSeT pin, you may be able to share this with your microcontroller reset pin but if you can, connect it to a digital pin.
- BUSY - this is the e-Ink busy detect pin, and is optional if you don't want to connect the pin (in which case the code will just wait an approximate number of seconds)
The FeatherWing eInk Display and eInk Feather Friend are a little more compact but have just about the same pins as the breakout
- SPI MOSI/MISO/SCK are on the FeatherWing SPI connection pads
SD CS, SRAM CS, EINK CS and DC are in order after the two I2C pins. The numbers of the pins these correspond to will differ from board to board. However, on 32u4/328p/M0/M4/nRF52840 and many other boards you will see the following connections
- SD CS to Pin D5
- SRAM CS to Pin D6
- EINK CS to Pin D9
- EINK DC to Pin D10
If you do not plan to use the SD card, you can cut the trace to SD CS. Likewise for SRAM CS.
The Reset pin for the E-Ink display is connected to an auto-reset circuit and also to the Feather Reset pin, so it will reset when you press the reset button.
The Busy pin is available on a breakout pad, you can solder it to a wire and connect to a pin if you need it - we figure most people will just use a fixed delay.
The 2.9" eInk FeatherWings also feature a few buttons. The exact pin the buttons are connected to can vary by the specific feather.
- A - this is button A and is connected to Pin D11 on many Feathers, but may vary.
- B - this is button B and is connected to Pin D12 on many Feathers, but may vary.
- C - this is button C and is connected to Pin D13 on many Feathers, but may vary.
- Reset - this button will reset the attached Feather.