SW4STM32 and SW4Linux fully supports the STM32MP1 asymmetric multicore Cortex/A7+M4 MPUs

   With System Workbench for Linux, Embedded Linux on the STM32MP1 family of MPUs from ST was never as simple to build and maintain, even for newcomers in the Linux world.
And, if you install System Workbench for Linux in System Workbench for STM32 you can seamlessly develop and debug asymmetric applications running partly on Linux, partly on the Cortex-M4.
You can get more information from the ac6-tools website and download two short videos (registration required) highlighting:

System Workbench for STM32

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nucleo f401re uart example

So now I can send data out via serial from the F401 nucleo board. Cool. But there is still one caveat:

The data I receive is distorted. Not all the char but roughly 3 out of 4.
For every char I send, I will receive one char.

I added delays sending between chars. same issue. So obviously no overfow issue.
I started switching baudrate. But no change.

I checked with my Saleae LA, hooking up to the TX/RX pins on the programmer board (right next to teh SWD header).
I see the same serial stream I see on the Host/PC side. So the corruption seems to already happen when the STM 32 F401 sends the data out.

I am using for testing the STM32 demo sample. So not sure what is wrong.

Anybody else encountered similar behaviour?
I never had such issue with my other ST board. So I am at loss right now.
Is there something wrong with the initialization of the chip?