NRF52840 USB_CDC_ACM + UART

Question

Hi, 
 I'm trying to combine serial UART functionality into the USBD_BLE_UART example. The goal is to send data in/out to the hardware UART as well. 
 I started off by loading the USBD_BLE_UART example, then added the UART functions from the UART peripheral example. Build was successful, but when executing, I get a NRF_INVALID_STATE error. I can only get the firmware to run without errors by commenting out the uart_init() function, but then the UART will not function if I do so. 
 It seems that the error is caused in APP_UART_FIFO, under nrfx_drv_init. 
 I'm using SES 3.34b, with SDKv15. 
 Any help appreciated.

Sigurd · Accepted Answer

Hi, 
 I assume that you are printing "Communication error occurred while handling UART." when you get the APP_UART_COMMUNICATION_ERROR event. 
 For APP_UART_COMMUNICATION_ERROR, the error-field contains the value in the ERRORSRC register for the UART peripheral. 
 12 in binary is 1100, so looking at the ERRORSRC r egister you are getting a Break condition and Framing error. 
 Are you receiving anything over UART? Could you check with a signal analyzer or oscilloscope ? 
 Is this a nRF52840-DK or a custom board? 
 How does your uart_init() function looks like ?

Julian · Answer

Hi Sigurd, 
 I have found the cause of this issue. When you asked about my uart_init() function , I went through it again and sure enough, the RX & TX pins are initialized wrongly. Sorry for such a newbie mistake. 
 I'd like to express my appreciation for your in-depth explanation on the UART SDK and hardware register. 
 Thank you for your outstanding support.

NRF52840 USB_CDC_ACM + UART

Top Replies