This note explains how to load files such as binary applications from Linux running on the target via UART. This is a useful procedure for those targets that do not provide an Ethernet link and have the serial console as the only communication channel.

On the host, activate the Cortex-M cross-development environment:

-bash-3.2$ pwd
/home/vlad/test/linux-cortexm-1.12.1
-bash-3.2$ . ./ACTIVATE.sh
-bash-3.2$

Create a simple "Hello, world" C application:

[host] $ cd /tmp
[host] $ vi test.c
#include <stdio.h>

void main(void)
{ printf("Hello, STM32F4\n");
}
~

Build the application for the Cortex-M target:

[host] $ arm-uclinuxeabi-gcc -o test test.c -I ${INSTALL_ROOT}/A2F/root/usr/include -mcpu=cortex-m3 -mthumb

Encode the application binary into an ASCII-only presentation so that the file can be transmitted over a serial line:

[host] $ uuencode test < test > test.encoded

You will require the uudecode application on the target in order to convert the ASCII-only file back into the application binary. Go to your project directory and enable uudecode in the target busybox:

[host] $ cd /home/vlad/test/linux-cortexm-1.12.1/projects/networking/
[host] $ make bmenuconfig

Go to Coreutils and enable uudecode:

Build the updated project:

[host] $ make
...

Load the resultant uImage (networking.uImage in the above example) to the target as described in http://www.emcraft.com/stm32f429discovery/loading-linux-images-over-uart.

On the host, make sure that the serial port you use for the target console is configured for 115.2 Bps:

[host] $ stty -F /dev/ttyUSB1
speed 115200 baud; line = 0;
eof = ^A; min = 1; time = 0;
ignbrk -brkint -icrnl -imaxbel
-opost -onlcr
-isig -icanon -iexten -echo -echoe

Start the target console:

[host] $ ./console-stm32f429.script
Connecting to /dev/ttyUSB1, speed 115200
Escape character: Ctrl-\ (ASCII 28, FS): enabled
Type the escape character followed by C to get back,
or followed by ? to see other options.
----------------------------------------------------

From the target, run the following to read a file from the serial console:

~ # cat > /test < /dev/ttyS0

Exit the target console (Ctrl-\ and then q in kermit).

On the host, send the encoded ASCII file to the serial port used for the target console:

[host] $ cd /tmp
[host] $ cat test.encoded > /dev/ttyUSB1

When the transfer command finishes, enter the target console again:

[host] $ ./console-stm32f429.script
Connecting to /dev/ttyUSB1, speed 115200
Escape character: Ctrl-\ (ASCII 28, FS): enabled
Type the escape character followed by C to get back,
or followed by ? to see other options.
----------------------------------------------------

Type Ctrl-C to interrupt the cat command:

^C

Run uudecode to convert the ASCII file back to the binary file:

~ # busybox uudecode /test.encoded

Change mode to allow running the application binary:

~ # chmod u+x test

Finally, run the application:

~ # ./test
Hello, STM32F4
~ #