UARTE: uart_fifo_read() - 4th byte always 0x00

Question

Hi, 
 I am not sure where to go next, so looking for some debug help. 
 Setup : I am using the 9160DK - the 52840 is being used as an ANT+ receiver, where it forwards on UARTE to 9160. 
 
 I have taken the code back to the basics, where I send 8 bytes containing 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 from the 52840 to the 9160, of which I receive the following on the 9160: 
 01 02 00 00 05 06 07 08 01 02 00 00 05 06 07 08 01 02 03 00 05 06 07 08 01 02 03 00 05 06 07 08 01 02 03 00 05 06 07 08 01 02 00 00 05 06 07 08 01 02 03 00 05 06 07 08 01 02 03 00 05 06 07 08 01 02 03 00 05 06 07 08 01 02 03 00 05 06 07 08 01 02 03 00 05 06 07 08 
 As can be seen from above, the 4th byte is always 0x00 and the 3rd byte is occasionally 0x00 - and I cant work out why. 52840 : 
 I am using nrf_libuarte_async_tx to send the 8 bytes - which appears to be working - as I can see most bytes correctly on the 9160. 9160 : 
 in uart_cb(): 
 
 while ( true ) 
 { 
 data_length = uart_fifo_read (x, &uart_buf, 1 ); 
 
 if (data_length != 1 ) { 
 printk ( " 
 " ); 
 break ; 
 } 
 printk ( " %02X " , uart_buf); 
 } 
 
 Other: * Both devices are set for, 115200 and HW-FC Off (or not set). 
 Before attaching my entire project here, is there anything obvious that could cause this to happen ? And, any ideas on the best way to debug this ? 
 
 regards 
 -brett

Georgiy Lutsenko · Answer

Hi all I had a similar issue. I am using 9160 and see the same problems with UART. I checked the sent data from another device with an analyzer. (The data is correct). But there is a problem on the 9160 side. For receiving and sending I use interrupts: 
 
 static void DtRS485_uartCallback ( const struct device * pDev , void * user_data ) 
 { 
 uart_irq_update ( pDev ); 
 
 if ( uart_irq_rx_ready ( pDev )) { 
 uint8_t data_length = 0 ; 
 data_length = uart_fifo_read ( pDev , uartBuf, sizeof (uartBuf)); 
 if ( spRxFifo != NULL ) { 
 if ( data_length > 0 ) { 
 DtFIFO_pushBuffer ( spRxFifo , uartBuf , data_length ); 
 
 } 
 } 
 } 
 if ( uart_irq_tx_ready ( skpUart )) { 
 
 uint16_t size = DtFIFO_availableForRead ( spTxFifo ); 
 if ( size > 0 ) { 
 DtGPIO_pinSet (DIR_RS485, true ); 
 DtFIFO_popBuffer ( spTxFifo , sBufTX , size ); 
 uart_fifo_fill ( pDev , sBufTX , size ); 
 } 
 if ( uart_irq_tx_complete ( skpUart )) { 
 uart_irq_tx_disable ( skpUart ); 
 DtGPIO_pinSet (DIR_RS485, false ); 
 } 
 } 
 } What is the UART interrupt priority? 
 Thanks. Best regards, 
 Georgiy