Another way is to use SEGGER RTT.
yapicoprobe dumps it to the USB serial bridge, but can go with debugprobe/openocd too.
This "prints" through SWD port leaving both UARTs free.void stdio_rtt_init (void)
Explicitly initialize stdin/stdout over RTT and add it to the current set of stdin/stdout drivers.
yapicoprobe dumps it to the USB serial bridge, but can go with debugprobe/openocd too.
Code:
0.000 (...) - (II) searching RTT_CB in 0x20000000..0x2007ffff, prev: 0x200007800.000 ( 0) - (II) ---- RTT_CB found at 0x200007800.001 ( 1) - (II) rtt_check_channel_from_target: 0 20000838 1024 0 10230.001 ( 0) - (II) rtt_check_channel_to_target : 0 20000828 16 0 015.6 Real Time Transfer (RTT)
Real Time Transfer (RTT) is an interface specified by SEGGER based on basic memory reads and writes to transfer data bidirectionally between target and host. The specification is independent of the target architecture. Every target that supports so called "background memory access", which means that the target memory can be accessed by the debugger while the target is running, can be used. This interface is especially of interest for targets without Serial Wire Output (SWO), such as ARM Cortex-M0, or where semihosting is not applicable because of real-time constraints.
Statistics: Posted by gmx — Mon Jan 26, 2026 1:37 am