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Problemwith SWD debugging on STM32L011D4P6

Question asked by rhodes.keith on Nov 22, 2016
Latest reply on Nov 24, 2016 by rhodes.keith

We are bringing up a new design using this CPU. Aside from other issues, we have an inconsistency between different boards when trying to program using SWD. 

On one working board, the SWD clock (pin 2 on the 10 pin JTAG connector) properly shows a clean signal. The circuit connects PA14 on the CPU to pin 2 of the 10 pin JTAG connector.

On other boards, it looks like someone else is driving this pin. On the scope, it shows 2 or 3 different levels of the signal, like the CPU is driving it for some reason.

Could this be that PA14 has been programmed to the Alternate function by default? Is there a way to reset the CPU so that the SWD pins work properly during reset/download?

We've used other STM32F parts and not had the same issues as the STM32L0 part.