Hello
I am using am5718 custom board.
I want to communicate rs485 using am5718 uart4.
The RS-485 control pin (RE, DE) pin uses GPIO.
But there is a problem.
RS-485 control pins (RE, DE) are not connected to uart4_rts, uart4_cts, so txd and rxd lines cannot be controlled. If you try to write after controlling a simple gpio, there is a problem because the time when the write is completed is not known.
Is there any way to use rs-485 without rts, cts pin?
Hi, Michael Erdahl
I solved this problem through my own debugging.
The problem is that UART TX works through FIFO management through DMA.
Therefore, the problem was that the CPU judged that the operation had been completed and controlled the TX pin, but the DMA was actually performing the TX operation, so if the TX pin was controlled, it would be disabled before all data was sent.
So, in order to solve the problem, if the TX_SR_E register is empty while the TX_SR_E register is in the middle of viewing the TRM document, check that the value is changed by IRQ and wait until the register value becomes empty before ending TX and change it to pin control. I did it.
