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 I got things sorted. As Vik pointed out the serial interface 2 (pa2/pa3) is routed through the virtual com interface of th eprogrammmer’s USB interface. For those of you who are using Linux. it will be /dev/ttyACM0. So a simple cat /dev/ttyACM0 should echo all printf send from the foirmware side. in Fedora 24 or earlier there is something called ModemManager that gets in your way. Things run more smoothly if you disable it. the following worked for me:

systemctl status dbus-org.freedesktop.ModemManager1.service
systemctl disable dbus-org.freedesktop.ModemManager1.service
the easiet is now to reboot so Network manager stops using the ModemManager.

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