Cannot send and receive on the same UART

[morganrallen]

It appears the serial interface cannot send and receive on the same UART.

The behavior can be see in esp-idf/examples/peripherals/uart/uart_events

Loading this example on a real ESP32 with a USB bridge connected to UART_0 anything typed on the terminal will be echo with uart_write_bytes and a ESP_LOGI call will be made on the default CONSOLE_UART, also UART_0

Loading this same example in qemu_esp32 will do nothing. But if uart_events/main/uart_events_example_main.c is edited to change...

#define EX_UART_NUM UART_NUM_0

to

#define EX_UART_NUM UART_NUM_1

It will work using two instances of nc connected to 8880 and 8881. In this case, anything typed into 8881 will be printed to 8880

[morganrallen]

This is on Ubuntu 19.04 running with qemu-system-xtensa -d guest_errors,unimp -cpu esp32 -M esp32 -m 4M -s

[Ebiroll]

Maybe
nc 127.0.0.1 8881 | nc 127.0.0.1 8880 | cat <&0
¢ould have worked as a bridge. I will test this later
However this does not solve the problem.

[Ebiroll]

OK. You are right. I will check this later.
The qemu uart emulation needs some fixing and this is a good example.

[morganrallen]

OK! Thanks @Ebiroll let me know if there is any other details I can help with.
I have an upcoming project with a large scale text interface that's I prefer not to have to flash
for every minor update. Look forward to digging into qemu-esp32 more. Thanks.

[Ebiroll]

Good idea. it will probably save you lots of time not having to flash constantly. You should also look at the possibility to run the qemu gdb debugger as it gives you a quick way of finding logic errors and stepping into the esp-idf code.