nrf52832 waveshare e-paper display spi driver help

[karinca]

Hi,

we are trying to use waveshare 2.9 epaper display with nrf52832, converted stm32 sample code to nrf52 with no luck. It seems we can not send command and data correctly to the display, it is not responding back via Busy line and program hangs on while loop. Can anybody help about this? We are using sdk 15's spi example with segger embedded studio.

I attached the code.spi.zip

[Håkon Alseth]

Hi,

 

The BUSY pin is an output (LOW = busy, HIGH = idle) from the e-paper, as stated in the datasheet, chapter 6: https://www.waveshare.com/w/upload/e/e6/2.9inch_e-Paper_Datasheet.pdf 

Note 6-4: This pin (BUSY) is Busy state output pin. When Busy is Low the operation of chip should not be interrupted and any commands should not be issued to the module. The driver IC will put Busy pin Low when the driver IC is working such as: ...

 

Given the above info, it looks like this pin shall be LOW when busy, but in your firmware, you seem to be looping over it incorrectly:

/**
 *  @brief: Wait until the busy_pin goes LOW
 */
void EPD_WaitUntilIdle(EPD* epd) {
  while(EPD_DigitalRead(epd, epd->busy_pin) == HIGH) {      //0: busy, 1: idle
    EPD_DelayMs(epd, 100);
    bsp_board_led_invert(BSP_BOARD_LED_0);
  }      
}

You need to set the loop to "== LOW" to loop while it's busy.

 

Best regards,

Håkon

[karinca]

this code is from their stm32 sample, it is working perfectly on stm32f1 uc. I think they wrote a wrong definitoın on function and documentation, this works as it is. I think something's wrong with the spi communication. I ask waveshare about nrf52 code but no response.

[Håkon Alseth]

Documentation states that you should use SPI mode 0, which you are.

Scope your lines (especially the BUSY line) and see if you see anything out of the ordinary.