UART timeout and timeout_char is not working in ESP32
Hi,
I noticed that UART timeout_char is not working. Regardless of the value of this parameter, UART always waits for around 8x the time of a character to identify that communication has ended.
With the help of a forum contributor, we were able to locate and fix the problem.
In the machine_uart.c we add the following command to line 208:
uart_set_rx_timeout(self->uart_num, self->timeout_char);
==================================================
Now that code snippet looked like this:
// set timeout_char
// make sure it is at least as long as a whole character (13 bits to be safe)
self->timeout_char = args[ARG_timeout_char].u_int;
uint32_t min_timeout_char = 13000 / baudrate + 1;
if (self->timeout_char < min_timeout_char) {
self->timeout_char = min_timeout_char;
}
uart_set_rx_timeout(self->uart_num, self->timeout_char);
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I don't know if timeouts have been disabled for a specific reason, but I would like to report that this minor fix resolves the issue, at least for timeout_char.
rp2: Add timeout and invert to the machine.uart class
This is a first attempt. It works, timeout and timeout_chars can be set and the object is properly printed, but there is an inherent problem in the way, machine_uart_read() and maybe machine_uart_write() is called. The problem is, when .e.g at uart.read() the numbers requested is larger than the ones in the FIFO. And that is different to e.g. the esp32 port.
Situation ESP32 RP2
request == present OK OK
none requested OK Error
request > present OK Error
What happens is, that on the RP2, if machine_uart_read() returns less than the initially requested bytes, it will be called again with the remaining number, which will then run into a timeout. On ESP32, the caller is just happy with what it got and returns to the top level. When uart.read() is called without an argument, the size at the machine_uart_read() is 256.
So the stream algorithm behaves different. machine_uart_read() is called different in these two ports.
As a temporary fix, the function machine_uart_read() returns on timeout without an error and with the numbers of bytes read.