4.3 inch e-Paper Display

Scripts to display vector shapes, BMP images and texts on WaveShare 4.3 inch e-paper display module via command-line instead of the Windows-only tools provided by the manufacture.

epd.py is based on the Arduino/C++ library provided by the manufacture.

4_level_gray_4bpp_BMP_converter.py is the solution to my question on StackExchange about converting images for the e-paper display. It relies on imagemagick for preprocessing the pixels and pipe into the converter as input.

Execute ./convert_to_grayscale.sh <source_image> to convert the source image to BMP format.

The outcome is a BMP image with the following attributes:

• indexed colours - 00 00 00 00/55 55 55 00/AA AA AA 00/FF FF FF 00
• 2bbp grayscale - i.e. 00/01/10/11, but
• 4bpp little-endian per pixel - i.e. 00 00/01 00/10 00/11 00
• each row of pixels is aligned to 4 bytes or 8 pixels

Interact With the e-Paper Display

>>> from epd import *
>>> help()              # prints help message which details all available functions
...
>>> epd_connect()       # must initiate a connection first, and then send commands to EPD
> EPD connected
> EPD handshake
...                     # whatever you want to do with EPD
>>> epd_disconnect()    # a clean finish after use

TCP/IP Support

The original e-paper display does not have TCP/IP support. I added an ESP8266 module to it as a TCP-serial relay and it works pretty well. epd_connect() will try TCP connection first, else falls back to serial port. All function calls are the same for TCP/IP or serial connection, except I have not implemented read-reply via TCP/IP. i.e. no VERBOSE mode for TCP/IP connection.

The baud rate should not be changed while connected via TCP/IP, as the WiFi module defaults to 115200 bps which does not change with the e-paper display.

Notes on File Management

The manufacture's manual isn't very clear about this. I consulted their technical support regarding how to remove the preloaded files, but the answer he gave some isn't the fact by my experiments. So here's my conclusion:

• The 128MB internal storage is partitioned into 48MB for fonts and 80MB for images (according to the manual, unverified)
• When calling the import functions (one for fonts and one for images), the relevant internal partition gets CLEARED and the fonts or images in the root directory of the SD card are copied over.
• Valid fonts or images are determined by the file names:
  • GBK32.FON,GBK48.FON and GBK64.FON for fonts
  • capital letters and digits followed by .BMP for images. Note that the total length of file names must be no more than 10 chracters including .BMP.
• If no valid font or image is found on SD card, the import functions will just clear the relevant internal storage.

# Example: to import images
# insert SD card
> epd_set_memory_sd()
> epd_import_pic()
> epd_set_memory_nand()
# remove SD card

Error Codes

0       Invalid command
1       SD card initiation failed
2       Invalid arguments
3       SD card not inserted
4       File not found
20      Validation failed
21      Invalid frame
250     Undefined error