E-Paper Displays, Pros and Cons

I got an e-Paper display to experiment with, the  2.9" SPI module I choose, the Amazon warehouse price turned out to be near $2 cheaper than the Chinese maker's store price, strange...

 E-Paper technology uses no backlight, it gives the appearance of paper using colored particles suspended in oil, they are low power devices, in fact they retain an image with no electrical connection.  The disadvantage of this sort of electro-mechanical thing moving around particles is a slow update rate, standard black and white displays like used in ebook readers update a page in about 2 seconds. which is tolarable for just advancing an ebook page, but the slow responce makes normal user interface designs clumsy.

Waveshare.com is a big supplier of raw displays an display modules in several forms.  The generic SPI module I chose was about $5 less than the Raspberry Pi hat version and is compatible with several devices. The various waveshare modules appear to use the same basic circuit, they include universal interface Pi Hats and Arduino Shiends, generic SPI boards and an ESP-32 board, which is an attactive choice for low current battery operated applications.

Black and white displays are considered "2 Color",  I choose a Black, White and Red 2 color display, not realising that they are usable only for more specialized applications due to the 15 second image update time (the red color apparantly comes from a larger particle, shuffling the different particles around is challenging.)

2 color vs 3 color differences

                                                                 2 COLOR                                   3 COLOR
Screen update time                                   2 Seconds                                    15 secons                       
Opeerating Temperature                          50°C (122°F)                              40°C (104°F)
Transport Temp.                                      -25~70°C                                      -25~60°C   
 Burn-in prevention                                      ---                                         Update every 24 hrs 
Partial update, fast no flicker                on some 2 color                                        ---                  



Here's a micro photo of a Kindle 3 display showing the individual ink particles that make an image.





Here's the complete Waveshare e-Paper module selection guide, showing the dramatic slowing of update time for 3 color displays vs Black and White.
Part NumberColorsGray ScaleResolutionDisplay size (mm)Outline Dimension (mm)Full Refresh Time (s)Partial RefreshPi Header1Interface
1.54inch e-Paper Module black, white 2 200x200 27.60 × 27.60 48.0 × 33.0       2 √ × SPI
1.54inch e-Paper Module (B) red, black, white 2 200x200 27.60 × 27.60 48.0 × 33.0       8 × × SPI
1.54inch e-Paper Module (C) yellow, black, white 2 152x152 27.51 × 27.51 48.0 × 33.0       27 × × SPI
2.13inch e-Paper HAT black, white 2 250x122 48.55 × 23.71 65.0 × 30.2       2 √ √ SPI
2.13inch e-Paper HAT (B) red, black, white 2 212x104 48.55 × 23.71 65.0 × 30.2       15 × √ SPI
2.13inch e-Paper HAT (C) yellow, black, white 2 212x104 48.55 × 23.71 65.0 × 30.2       15 × √ SPI
2.13inch e-Paper HAT (D) black, white 2 212x104 48.55 × 23.71 59.2 × 29.2       2 √ √ SPI
2.7inch e-Paper HAT black, white 2 264x176 57.29 × 38.19 85.0 × 56.0       6 × √ SPI
2.7inch e-Paper HAT (B) red, black, white 2 264x176 57.29 × 38.19 85.0 × 56.0       15 × √ SPI
2.9inch e-Paper Module black, white 2 296x128 66.89 × 29.05 89.5 × 38.0       2 √ × SPI
2.9inch e-Paper Module (B) red, black, white 2 296x128 66.89 × 29.05 89.5 × 38.0       15 × × SPI
2.9inch e-Paper Module (C) yellow, black, white 2 296x128 66.89 × 29.05 89.5 × 38.0       15 × × SPI
2.9inch e-Paper HAT (D) black, white 2 296x128 66.90 × 29.06 79.0 × 36.7       2 √ √ SPI
4.2inch e-Paper Module black, white 2 400x300 84.80 × 63.60 103.0 × 78.5       4 × × SPI
4.2inch e-Paper Module (B) red, black, white 2 400x300 84.80 × 63.60 103.0 × 78.5       15 × × SPI
4.2inch e-Paper Module (C) yellow, black, white 2 400x300 84.80 × 63.60 103.0 × 78.5       15 × × SPI
4.3inch e-Paper UART Module black, white 4 800x600 88.00 × 66.00 118.0 × 75.0       1.5 × × UART
5.83inch e-Paper HAT black, white 2 600x448 118.8 × 88.26 125.4 × 99.5       3.5 × √ SPI
5.83inch e-Paper HAT (B) red, black, white 2 600x448 118.8 × 88.26 125.4 × 99.5       14 × √ SPI
5.83inch e-Paper HAT (C) yellow, black, white 2 600x448 118.8 × 88.26 125.4 × 99.5       26 × √ SPI
6inch e-Paper HAT black, white 16 800x600 122.4 × 90.6 138.4 × 101.8       <1 √ √ USB/SPI/
I80/I2C
7.5inch e-Paper HAT black, white 2 640x384 163.20 × 97.92 170.2 × 111.2       6 × √ SPI
7.5inch e-Paper HAT (B) red, black, white 2 640x384 163.20 × 97.92 170.2 × 111.2       16 × √ SPI
7.5inch e-Paper HAT (C) yellow, black, white 2 640x384 163.20 × 97.92 170.2 × 111.2       16 × √ SPI
7.8inch e-Paper HAT black, white 16 1872×1404 158.18 × 118.64 173.8 × 127.6       <1 √ √ USB/SPI/
I80/I2C
9.7inch e-Paper HAT black, white 16 1200x825 202.8 × 139.43 218.8×156.4       <1 √ √ USB/SPI/
I80/I2C
10.3inch e-Paper HAT (D) black, white 16 1872×1404 209.66 × 157.25 227.7 × 165.8       <1 √ √ USB/SPI/
I80/I2C

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