Xiao nRF52840 - Sense dual displays

Hi all,

I’m working with the Xiao nRF52840 BLE Sense. I’m attempting to get 2 displays working, one update at a time. I.E. Update display 1, put to sleep/pullup CS/RST, update display 2… etc

I have a waveshare epaper 1.54" and a waveshare lcd 1.28". They work independently (same .ino code), but when both are physically connected the lcd won’t do anything (backlight is on). Occasionally I can get the lcd to work but inconsistent.

What works;

Using both drivers integrated into the same sketch - each display works if the other is disconnected.

Using stand alone demo from waveshare for the 1.28" lcd with the epaper connected (lcd works)

Using stand alone demo from waveshare for the 1.54" epaper - WITHOUT the 1.28" LCD connected

Pins:

I have CS and Reset on “different” pins so they should not conflict. Again they both work independently with same code.

Further: I have the epaper code up front to test and then put it to sleep BEFORE the LCD code… I have tried to pullup the RST and CS pins (display is active when low) on the LCD display in hopes the epaper would work. Occasionally I will see the epaper flicker but doesn’t do what it needs.

I’ve checked the 3.3v power and it should easily handle both displays.

Any suggestions?

Which bus are you using to connect the displays?

  • I²C: check the addresses, they should be different
  • SPI: disconnect the unused MISO lines, as they may interfere when the device is not used

A great tool to help you is a logic analyser.

Ok so this is the update. I was able to get both displays working. The problem was these are two different types of displays. Epaper and lcd. The lcd has a backlight on the last pin (on the display) The epaper has a busy in the same respective position. For some reason my brain wired them to the same pin. Basically the duty cycle on the backlight pin drove the epaper nuts.

I currently have separate pins CS/RST and BUSY and BACKLIGHT.