Re: MCUMGR - sends responses to wrong port

Carles Cufi

Hi Lawrence,


Try instead using the .dts in your board, or add an overlay, and change this line:


zephyr,uart-mcumgr = &uart0;






From: devel@... <devel@...> On Behalf Of Lawrence King via
Sent: 15 July 2020 23:20
To: zephyr-devel@...; Zephyr-users@...
Subject: [Zephyr-devel] MCUMGR - sends responses to wrong port


Dear All:


I am trying to setup mcumgr to allow code download over a serial port and use the shell. In this case I have 2 serial ports in play.


The first serial port is where printk() sends messages. I also have a simple command parser on the port that interprets single letter commands. This printk and my command parser work as expected.


The second serial port is running a shell. Commands like ‘help’ and ‘fs ls’ work as expected, output appears on the second port. However when I attempt to send a file or image update using mcumgr to the second serial port, it doesn’t work. The initial packet arrives on the serial port, smp_shell recognizes the packet, formulates a response, and then sends the response to the first serial port, not the second serial port as it should. LOG messages also come out on the second port as expected.


I chased the  problem as far as I can. In smp_shell.c the function smp_shell_tx_raw() always sends the packet via k_str_out(). It should be sending the packet back by shell_print(). Unfortunately the function smp_shell_tx_raw doesn’t have access to the handle for the shell.


I did try setting CONFIG_UART_MCUMGR_ON_DEV_NAME but k_str_out() ignores this setting….


Any suggestions on how to fix this? Or am I doing something wrong?



Lawrence King

Principal Developer

Connected Transport Market Unit



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