Golang and Arduino

Small arduino and golang programs

ansi C unions on arduino

After some time of googling, i found interesting solution, how to get and set pins as bits in arduino


union myunion {
    struct {
        unsigned int b7: 1;
        unsigned int b6: 1;
        unsigned int b5: 1;
        unsigned int b4: 1;
        unsigned int b3: 1;
        unsigned int b2: 1;
        unsigned int b1: 1;
        unsigned int b0: 1;
    };
    unsigned int num;
} mu;

with this union with struct, we can read pins to 1 big number invidual bits and display it on for example - led's in binary.


mu.b0 = digitalRead(2);
mu.b1 = digitalRead(3);
mu.b2 = digitalRead(4);
mu.b3 = digitalRead(5);
mu.b4 = digitalRead(6);
mu.b5 = digitalRead(7);
mu.b6 = digitalRead(8);
mu.b7 = digitalRead(9);

and vuola, now we can get number with "mu.num" depending on HIGH pins 


Serial.println(mu.num);

and in reverse, we can set "mu.num = 127" and write individual bits to pins.


digitalWrite(mu.b0);
digitalWrite(mu.b1);
digitalWrite(mu.b2);
digitalWrite(mu.b3);
digitalWrite(mu.b4);
digitalWrite(mu.b5);
digitalWrite(mu.b6);
digitalWrite(mu.b7);

whole program:


// parallel to serial
// serial to parallel
union mu1 {
    struct {
        unsigned int b7: 1;
        unsigned int b6: 1;
        unsigned int b5: 1;
        unsigned int b4: 1;
        unsigned int b3: 1;
        unsigned int b2: 1;
        unsigned int b1: 1;
        unsigned int b0: 1;
    };
    unsigned int num;
} mu;

void setup() {
  Serial.begin(9600);
}

void loop() {
  mu.b0 = digitalRead(2); // switch 1
  mu.b1 = digitalRead(3); // switch 2
  mu.b2 = digitalRead(4); // switch 3
  mu.b3 = digitalRead(5); // switch 4
  mu.b4 = digitalRead(6); // switch 5
  mu.b5 = digitalRead(7); // switch 6
  mu.b6 = digitalRead(8); // switch 7
  mu.b7 = digitalRead(9); // switch 8

  Serial.println(mu.num);
  delay(5000);
}

thats it. union acts as "shift in" and "shift out" register, if you set mu.num than you can read individual bits(pins) if you set pins you can read mu.num and it works then like shift in register.

arduino read serial command and parse to variables

You can send command without any libraries to arduino. in this example "message" ( protocol) is "2 chars + number + number" -> "GO 123 -512" 


void setup() { Serial.begin(9600); } void loop() {
// check if something on Serial if(Serial.available()) {
// define variables long number1, number2; char cmd[2]; memset(cmd, 0, 2);
// read data from Serial String s = Serial.readStringUntil('\n'); char buff[64]; memset(buff, 0, 64);
// convert string to char array s.toCharArray(buff, 64);
// parse cmd to variables sscanf(buff, "%2c %ld %ld",cmd, &number1, &number2); char pr[128]; memset(pr, 0, 128);
// print template to buffer sprintf(pr, "got 2 numbers from serial: %ld and %ld and command %s", number1, number2, cmd);
// print buffer back to Serial Serial.println(pr); } }

Golang sync cond example

golang sync cond working example


package main

import (
    "sync"
    "time"
)

var mu = sync.Mutex{}
var sc = sync.NewCond(&mu)

var setME string

func main() {
    go func() {
        for {

        }
    }()

    // start 10 gourintines

    for i := 0; i < 10; i++ {
        go func(i int) {
            println("go routine started")
            sc.L.Lock()
            sc.Wait()
            println(setME, "release", i)
            sc.L.Unlock()

        }(i)
    }
    time.Sleep(1 * time.Second)

    // set variable and
    // signal sync.cond to release 3 random locks
    // from waiting go routines

    for i := 0; i < 3; i++ {
        sc.L.Lock()
        setME = "test signal"
        sc.Signal()
        sc.L.Unlock()
    }
    time.Sleep(2 * time.Second)

    // release all waiting go routines to use global variable
    sc.L.Lock()
    setME = "test broadcast"
    sc.Broadcast()
    sc.L.Unlock()

    time.Sleep(3 * time.Second)
}