DMAC/reactor/needs_port/i2c/bus.go

// package i2c wraps the [i2c package] to interact with the i2c
// with devices on the bus
//
// [i2c package]: https://pkg.go.dev/periph.io/x/conn/v3/i2c#pkg-overview
package i2c

import (
	"FRMS/internal/pkg/logging"
	"bytes"
	"fmt"
	_ "log"
	"os/exec"
	"strconv"
	"strings"
)

// GetConnected returns a map of each device address and its current
// connection status.
func GetConnected(b int) (map[int]bool, error) {

	bus := strconv.Itoa(b)
	devices := make(map[int]bool) // only keys

	cmd := exec.Command("i2cdetect", "-y", "-r", bus)

	var out bytes.Buffer
	var errs bytes.Buffer
	cmd.Stderr = &errs
	cmd.Stdout = &out

	if err := cmd.Run(); err != nil {

		logging.Debug(
			logging.DError,
			"I2C scan error %v",
			errs.String(),
		)

		return devices, err
	}

	// parsing the command output
	outString := out.String()
	split := strings.SplitAfter(outString, ":")

	// 1st entry is reserved and ending is always \n##:
	split = split[1:]

	// create empty slice for all the devices
	for i, v := range split {
		lastDevice := strings.Index(v, "\n")

		trimmed := v[:lastDevice]
		trimmed = strings.Trim(trimmed, " ")

		count := strings.Split(trimmed, " ")

		for j, d := range count {
			// the first row has to be offset by 3 but after its just i*16 + j
			offset := j
			if i == 0 {
				offset += 3
			}

			addr := i*16 + offset

			if !strings.Contains(d, "--") && !strings.Contains(d, "UU") {
				devices[addr] = true
			}
		}
	}

	return devices, nil
}

// SendCmd sends an arbitrary command string to the device at addr on i2c bus b.
// Command will be converted from a string to bytes before
// attempting to be sent.
func SendCmd(b, addr int, command string) (string, error) {

	var cmd *exec.Cmd
	bus := strconv.Itoa(b)
	// default to an empty read
	operation := "r20"
	frmt_cmd := ""
	if command != "" {
		// command, do write
		operation = fmt.Sprintf("w%d", len(command)) // write
		// formatting cmd
		for _, char := range command {
			// loop over string
			frmt_cmd += fmt.Sprintf("0x%x", char)
		}
		cmd = exec.Command("i2ctransfer", "-y", bus, fmt.Sprintf("%s@0x%x", operation, addr), frmt_cmd)
	} else {
		// reading
		cmd = exec.Command("i2ctransfer", "-y", bus, fmt.Sprintf("%s@0x%x", operation, addr))
	}

	// execute command
	var out bytes.Buffer
	var errs bytes.Buffer
	cmd.Stderr = &errs
	cmd.Stdout = &out

	if err := cmd.Run(); err != nil {

		logging.Debug(logging.DError, "I2C command error %v", err)

		return "", err
	}

	return out.String(), nil
}