Hi team,
Use SCIB for 485 half-duplex transmission, SCIB does not use interrupts, the main flow always queries, and the baud rate is 115200. The upper computer (PCs) periodically sends one byte of data to the TMS320F28374S, which always queries the buffer in while(1). When data is detected, the receive enable is turned off (RXENA) and the received data is sent, then the receive enable is turned on. Loop like this. Query frequency < 500 us.
Based on the waveform above, the yellow waveform represents the level of rollover when data is received and the blue color is the 485_RD (485 transmit and receive switching) signal. The receive state is pulled low and then pulled high when data needs to be transmitted, and the green waveform (485_RXD) is pulled low when data is transmitted. If the SCI receive enable (RXENA) is not turned off, the SCI receives the data that RX is pulled low at the time of transmission, resulting in RXError and FE.
So when the customer sends in the code, they turn the receive RXENA off, and then turn the receive enable on after the delivery is complete. However, the test found that the DSP still received this data for the off receive enable. Why is this? The customer also used the F28335 to test it, and it's the same issue.
Could you help check this case? Thanks.
Best Regards,
Cherry
