UART Receive Problem

[yoyicue]

I can not Receive more than 1 Byte of data with UART.
I sent 4 Byte:

Code: Select all

>>> u = pyb.UART(4, 9600)
>>> u.recv(1)
b'a'

I sent 4 Byte again:

Code: Select all

>>> u.recv(4)
Traceback (most recent call last):
  File "<stdin>", line 0, in <module>
Exception: HAL_UART_Receive failed with code 3

What is wrong?

[dhylands]

Error 3 is a timeout. Since you didn't specify a timeout on your recv, it uses a default of 5 seconds.

It means that 4 characters didn't arrive within 5 seconds.

I'm not sure what the intended behaviour is for receiving less than the number of characters that you asked for. Generally I would have expected that if only 3 characters arrived, then it would return those 3 character rather than throwing an exception.

So, for the time being, you should read one character at a time. I'll post an issue and see what Damien says.

[Damien]

As dhylands say, it's timing out because 4 characters were not available.

To check for a timeout you can do:

try:
c = uart.recv(1)
except:
print('timeout')

This will work for getting 1 character, but if you want to get more than 1 you will need to put the above in a loop.

We'll work on this problem to get it fixed properly.