[riot-notifications] [RIOT-OS/RIOT] cpu/stm32_common/periph/gpio: Pull-down on gpio_init_af (#12236)

Thomas Stilwell notifications at github.com
Mon Sep 16 02:32:27 CEST 2019


Ok so just for dramatic effect - here's one example of what it can look like when uart rx is floating:
```
shell: command not found: �K�����1������ct
1 > 
1 > shel��닁f��r��
shell: command not found: shel��닁f��r��
0��[shell] unhandled control character ^@ (0x00)
��[shell] unhandled control character ^@ (0x00)
+��1��[shell] unhandled control character ^@ (0x00)
�[shell] unhandled control character ^A (0x01)
[shell] unhandled control character ^B (0x02)
e�nho��c ^���uZX[shell] unhandled control character ^@ (0x00)
��,+[shell] unhandled control character ^E (0x05)
�[shell] unhandled control character ^@ (0x00)
�[shell] unhandled control character ^E (0x05)
1 > +j�[GOMACH] TX queue full, drop packet.
�[shell] unhandled control character ^V (0x16)
�[shell] unhandled control character ^Q (0x11)
�ɽ���[shell] unhandled control character ^E (0x05)
^@ ��[shell]�ed contr�,W��^A .���u��[shell] unhandled control character ^Z (0x1a)
���ɽ�.�[shell] unhandled control character ^A (0x01)
��Y[GOMACH] TX queue full, drop packet.
[GOMACH] TX queue full, drop packet.
����[shell] unhandled control character ^@ (0x00)
�[shell] unhandled control character ^W (0x17)
�[shell] unhandled control character ^@ (0x00)
�
1 > �[shell] unhandled control character ^A (0x01)
�i���,���S���.��ױ[shell] unhandled control character ^@ (0x00)
��[shell] unhandled control character ^@ (0x00)
��[shell] unhandled control character ^@ (0x00)
shell: command not found: �������
1 > �d�[shell] unhandled control character ^I (0x09)
)�+�k�[shell] unhandled control character ^K (0x0b)
�=�(�[shell] unhandled control character ^A (0x01)
[shell] unhandled control character ^L (0x0c)
�[shell] unhandled control character ^I (0x09)
�[shell] unhandled control character ^K (0x0b)
�9���[shell] unhandled control character ^K (0x0b)
�[shell] unhandled control character ^I (0x09)
!�+�
shell: command not found: �d�)�+�k���������=�(����9�������0��!�+�
1 > �[shell] unhandled control character ^@ (0x00)
[shell] unhandled control character ^Z (0x1a)
����0������[shell] unhandled control character ^Z (0x1a)
��Ʌ�0)
shell: command not found: �������.�¹�0x0�+����0��������Ʌ�0)
1 > �handl�[shell] unhandled control character ^@ (0x00)
�[shell] unhandled control character ^@ (0x00)
�[shell] unhandled control character ^A (0x01)
)
shell: command not found: �handl���)
1 > [shY��X[shell] unhandled control character ^@ (0x00)
er��[shel[shell] unhandled control character ^A (0x01)
������][shell] unhandled control character ^K (0x0b)
��[shell] unhandled control character ^K (0x0b)
ac���[shell] unhandled control character ^A (0x01)
�[[shell] unhandled control character ^K (0x0b)
+������haracLJR���������X��JR��
```

And here's what it looks like after enabling the pullup:
```
>
```

Big difference ;)

Of course I did intentionally arrange for the effect to be extreme for demonstration purposes. If you want to reproduce this extreme result, just connect a wire to a uart rx pin without connecting the other end of the wire to anything. If necessary, brush the loose end of the wire with your finger. This should generate plenty of buggy behavior for testing purposes. The pullup will fix it entirely.

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