Real-time Visualization with rtplot and debug-link

1. Build rtplot example

Download the example files using:

./scripts/download-examples.sh

Enable debug-link task in user/task/task.mk

# Uncomment the line
SRC += $(PROJ_ROOT)/user/tasks/debug_task.c

Rebuild the source code:

make all

Install rtplot tool to the system:

cd tools/rtplot/
make install

2. Run rtplot example with QEMU

First, execute the following command to launch the Tenok with QEMU:

make qemu

The output should be similar to the following:

char device redirected to /dev/pts/X (label serial1)
char device redirected to /dev/pts/Y (label serial2)
[    0.001000000] Tenok RTOS (built time: 11:14:41 Nov  8 2023)
[    0.001000000] Machine model: stm32f407
[    0.006000000] chardev serial0: console
[    0.008000000] chardev serial1: mavlink
[    0.008000000] chardev serial2: debug-link
[    0.008000000] blkdev rom: romfs storage
type `help' for help
user@stm32f407:/$

According to the output, serial2 (debug-link) is redirceted to /dev/pts/Y.

Now open another terminal and execute the following command:

cd tools/rtplot/
make rtplot

After the rtplot window shows up, select /dev/pts/Y port, test message then click the connect button. The user should expect to see some real-time data plotting on the screen.

3. Define debug-link message

Tenok uses a metalanguage to define messages for debug visualization, this message prorocol is called the Debug-Link. All message files should named as *.msg and by default they should be placed in the msg/ directory.

To define a variable, the user can use the following syntax:

type variable "description"

For array, the syntax is:

type array[size] "description"

For example, in test.msg (provided by the ./scripts/download-examples.sh), the messages are defined as:

uint32_t time     "boot time"
float    accel[3] "acceleration"
float    q[4]     "quaternion"

The supported types are:

• bool
• uint8_t
• int8_t
• uint16_t
• int16_t
• uint32_t
• int32_t
• uint64_t
• int64_t
• float
• double

The third description field of the message definition is optional, but it is recommended to not neglect it as it will show up in the real-time plotting graph.

When user execute make all to build the code, the Makefile target calls the msggen tool to generate C code and YAML files. The user should pack their on-board data with the generated C functions and send out the message to their computer via I/Os like USART, USB, etc. To visualize the messages, the user can then use another built-in tool called rtplot, which reads the message definitions from the generated YAML files.

The following code illustrates a basic C code implementation for sending message:

...
#include "debug_link_test_msg.h"
 
...
void debug_link_task(void)
{
    setprogname("debug link");
 
    int debug_link_fd = open("/dev/serial2", O_RDWR);
...
    debug_link_msg_test_t msg = {
        .time = 0,
        .accel = {1.0f, 2.0f, 3.0f},
        .q = {1.0f, 0.0f, 0.0f, 0.0f}
    };
 
    uint8_t buf[100];
 
    while(1) {
        size_t size = pack_debug_link_test_msg(&msg, buf);
        write(debug_link_fd, buf, size);
...
        usleep(10000); //100Hz (10ms)
    }
}
 
HOOK_USER_TASK(debug_link_task, 3, 1024);

The full example code can be found in user/task/debug/debug_task.c.