I tested it on my CERB40 board which has UART5 exposed (and has no sdcard).
It seems to be working fine for that.
You may want to compare your code with mine to see where you're doing things differently. I think you were missing the IRQ handler whcih would cause the board to hang as soon as an imcoming character was received.
If I connect C12 to D2 then with the PR applied I see the following:
Code: Select all
Micro Python v1.4.3-74-g286ced4-dirty on 2015-05-31; Cerb40 with STM32F405RG Type "help()" for more information. >>> u5 = pyb.UART(5, 115200) >>> u5.write('This is a test') 14 >>> u5.read(7) b'This is' >>> u5.read(7) b' a test'