WiringPi是树莓派上比较好的一个开发库，是用C语言写的。使用cgo，我们可以在Go语言里方便的调用WiringPI的函数，于是我包装了一个WiringPi-Go，目前支持wiringPi的基本功能，硬件SPI协议驱动Nokia 5110屏幕，以及中断，未来还会增加PWM和I2C协议的支持。
下面是一个完整的使用例子，结合了之前的两个电路：链接1，链接2
通过push button可以切换液晶屏显示不同脚本的输出内容。
lcd_switch.go
package main
import (
. "github.com/hugozhu/rpi"
"github.com/hugozhu/rpi/pcd8544"
"log"
"os/exec"
"time"
)
const (
DIN = PIN_MOSI
SCLK = PIN_SCLK
DC = PIN_GPIO_2
RST = PIN_GPIO_0
CS = PIN_CE0
PUSHBUTTON = PIN_GPIO_6
CONTRAST = 40 //may need tweak for each Nokia 5110 screen
)
var screen_chan chan int
var TOTAL_MODES = 3
func init() {
WiringPiSetup()
pcd8544.LCDInit(SCLK, DIN, DC, CS, RST, CONTRAST)
screen_chan = make(chan int, 1)
}
func main() {
//a goroutine to check button push event
go func() {
last_time := time.Now().UnixNano() / 1000000
btn_pushed := 0
for pin := range WiringPiISR(PUSHBUTTON, INT_EDGE_FALLING) {
if pin > -1 {
n := time.Now().UnixNano() / 1000000
delta := n - last_time
if delta > 300 { //software debouncing
log.Println("btn pushed")
last_time = n
btn_pushed++
screen_chan <- btn_pushed % TOTAL_MODES //switch the screen display
}
}
}
}()
//a groutine to update display every 5 seconds
go loop_update_display()
//set screen 0 to be default display
screen_chan <- 0
ticker := time.NewTicker(5 * time.Second)
for {
<-ticker.C
screen_chan <- -1 //refresh current screen every 5 seconds
}
}
func loop_update_display() {
current_screen := 0
for screen := range screen_chan {
if screen >= 0 {
if screen != current_screen {
//btn pushed
current_screen = screen
display_loading()
}
}
switch current_screen {
case 0:
display_screen0()
case 1:
display_screen1()
case 2:
display_screen2()
}
}
}
func display_loading() {
pcd8544.LCDclear()
pcd8544.LCDdrawstring(0, 20, "Loading ...")
pcd8544.LCDdisplay()
}
func display_screen0() {
out, err := exec.Command("/bin/screen_0.sh").CombinedOutput()
if err != nil {
out = []byte(err.Error())
}
pcd8544.LCDclear()
pcd8544.LCDdrawstring(0, 0, string(out))
pcd8544.LCDdisplay()
}
func display_screen1() {
out, err := exec.Command("/bin/screen_1.sh").CombinedOutput()
if err != nil {
out = []byte(err.Error())
}
pcd8544.LCDclear()
pcd8544.LCDdrawstring(0, 0, string(out))
pcd8544.LCDdisplay()
}
func display_screen2() {
out, err := exec.Command("/bin/screen_2.sh").CombinedOutput()
if err != nil {
out = []byte(err.Error())
}
pcd8544.LCDclear()
pcd8544.LCDdrawstring(0, 0, string(out))
pcd8544.LCDdisplay()
}
/bin/screen_2.sh
#!/bin/bash
echo "Current IP:"
ifconfig | grep "inet " | awk '{print $2}'