Santek EZ Door Sign

The Santek EZ Door Sign is cordless e-ink display intended to be mounted outside of offices or rooms. It is capable of storing 5 custom images that can be displayed and rotated with the side button.

The 2.9" variant which I obtained has a resolution of 296 x 128 pixels and is capable of displaying black, white, and red.

Serial protocol

Background

Santek provides a Windows based app written in C# that is able to interact with the door signs. My goal is to have some Linux based device that can periodically update these displays (such as the weather or calendar events on an hourly basis). In order to do that, I will need to figure out how exactly this device talks via the USB port.

There are some GitHub projects that try to interface with this device already including https://github.com/m3m0r7/ez-door-sign in PHP and https://github.com/kenichi884/ezsign.py in Python. However, the documentation on the serial protocol is a bit lacking. Fortunately, the protocol doesn't seem too complicated.

Serial configuration

Use 9600 baud. No parity.

The display has to be on. Ensure that the blue LED is lit before trying to talk to it via serial.

Commands

Here are some of the supported commands by the display.

Command Type is 0 if it's a command that's sent to the display. It will be a 1 if it's data that's a response to a command made by the display.

Header	Command Type	Command ID	Data Length	Data	Chksum	Ending	Notes
0xBB	0x00	0x03	0x02	site-canvas	variable	0x7E	set image head data. This specifies which canvas you are overwriting. Data is always 2 bytes long, containing: site: slide number (0 through 4) canvas: Color canvas (0 or 1)
0xBB	0x01	0x03	0x01	0x01		0x7E	did set image head data succeed? Data should be 0x01
0xBB	0x00	0x04	0x12	column-bitmap	variable	0x7E	send image bitmap data by column. Data is always 18 bytes long. 2 for column number, 16 for bitmap data. Bitmap data here is based on the canvas setting in order to get that extra bit for color. Column: 2 bytes in decimal. (0 ~ 295) (0x00,0x00 ~ 0x01,0x27) Bitmap: 16 bytes. One bit per pixel makes 128 pixels This is how you can retrieve data for the 296x128 pixel display.
0xBB	0x01	0x04	0x01	0x01		0x7E	did send image row data succeed? Data should be 0x01
0xBB	0x00	0x05	0x04	site-canvas-column	variable	0x7E	Get image bitmap from display memory. Data is always 4 bytes long. Site: Slide number (0 through 4) Canvas: Color canvas (0 or 1) Column: 2 bytes. (0 ~ 295) To retrieve the actual color, you have to read both canvas See the response payload below.
0xBB	0x01	0x05	0x12	column-bitmap	variable	0x7E	Bitmap data received from a get command. The response message is always 24 bytes long. There are 18 bytes of payload data and is the same format as the send-image-column command. Column: 2 bytes. (0 ~ 295) Bitmap: 16 bytes. One bit per pixel makes 128 pixels
0xBB		0x06				0x7E	iap model
0xBB	0x00	0x07	0x01	0x00	0x08	0x7E	power off
0xBB	0x00	0x00	0x01	0xFE	0xFF	0x7E	next slide
0xBB	0x00	0x00	0x01	0xFF	0x00	0x7E	previous slide (called 'up' in C# code)
0xBB	0x00	0x00	0x01	site	site+1	0x7E	Redraws the slide (0 ~ 4)
0xBB	0x01	0x00	0x01	site			Redrew the slide ok.
0xBB	0x00	0x01	0x01	site	variable	0x7E	Check if site is blank. if returned 4th byte is 254, then isBlank is false
0xBB	0x01	0x01	0x01	site	variable	0x7E	site given bacak is 0xFE, meaning slide is not blank.

The checksum is calculated by summing everything

When reading data...

• read and discard until you see 187
• ???

Color data

The site-canvas-row data that you read/write using the commands above determine the color. Because we only use one bit per canvas, the canvas is pretty much how you define an additional bit per pixel.

	Canvas = 0	Canvas = 1	Color
Pixel bit value	0	0	Black
	1	0	White
	0	1	Red

For black and white only pictures, you can effectively ignore setting canvas=1.