How to create a tunnel between two half-duplex serial ports?

Question

I am working on an embedded project which includes two half duplex UARTS, and one full duplex UART.

UART1 is connected to Device A. UART2 is connected to Device B, and UART3 is connected to the PC. UART1 and UART2 are half-duplex, thus RX/TX modes have to be configured properly.

When a signal on UART1 is triggered, UART2 fetches some data from Device B. That data is put into a buffer, and then transmitted back to UART1, AND UART3. Device A consumes the data, and sends more items on UART1, which then has to be passed to UART2 for Device B to respond.

I was thinking about an efficient state machine that can handle the switching modes between TX/RX mode, and so far my UART code is interrupt driven. What would be some ways to tackle the flow of this program?

Answer 1

I don't think you will need a state machine for this case. Why not just hook up all interrupts accordingly and just forward anything received from one devivce to the other(s)?

You may want to include a TX (ring-)buffer to accomodate for different speeds of each UART and then just have a RX-ISR write the data received to the appropriate TX buffer(s), from where it will then be consumed by the other UARTs' UDRE-ISRs.