File content as of revision 3:08c16b8a78bf:

#include "mbed.h"
#include "cmsis_os.h"

DigitalOut StepLED(LED1);
DigitalOut CmdLED(LED2);
DigitalOut DirLED(LED3);

typedef struct {
    int steps;  // number of steps to take
    int speed;  // speed in steps/sec
    int accel;  // accelleration in steps/sec^2
    int maxspeed; // maximum speed in steps/sec
    int minspeed; // minimum speed in steps/sec
    bool dir;    // direction
} stepcmd;

osPoolDef(cmdpool, 16, stepcmd);
osPoolId cmdpool;

osMessageQDef(queue, 16, stepcmd);
osMessageQId  queue;

void read_thread (void const *args) {
    while (true) {
        osEvent evt = osMessageGet(queue, 0);
        if (evt.status == osEventMessage) {
            stepcmd *cmd = (stepcmd*)evt.value.p;
            DirLED = cmd->dir;
            StepLED = 1;
            osDelay(100);
            StepLED = 0;
            osPoolFree(cmdpool, cmd);
        } else { // assume no info available
            osDelay(100);
        }
        osDelay(100);
    }
}

osThreadDef(read_thread, osPriorityNormal, DEFAULT_STACK_SIZE);

int main (void) {
    cmdpool = osPoolCreate(osPool(cmdpool));
    queue = osMessageCreate(osMessageQ(queue), NULL);
    
    osThreadCreate(osThread(read_thread), NULL);
    bool mydir = true;
    while (true) {
        const float startspeed = 0.05;  // speed in m/s
        const float maxspeed = 2; // speed in m/s
        const float accel = 2; // accelleration in m/s^2
        const float distance = 1.26; // maximum distance on the rod in m
        const int steps = 36000; // steps per meter
        stepcmd *cmd = (stepcmd*)osPoolAlloc(cmdpool);
        cmd -> minspeed = int(startspeed * steps);
        cmd -> maxspeed = int(maxspeed * steps);
        cmd -> accel = int(accel * steps);
        cmd -> steps = int(distance * steps);
        cmd -> speed = cmd -> minspeed;
        cmd -> dir = mydir; 
        mydir = !mydir;
        osStatus res = osMessagePut(queue, (uint32_t)cmd, 0);
        while (res != osOK) {
            osDelay(500);
            res = osMessagePut(queue, (uint32_t)cmd, 0);
        }
        osDelay(1000);
        CmdLED = ! CmdLED;
    }
}