Go transceiver interface for RF-5V
The goal of the project is to provide simple burst packet transmission
The Manchester encoding is used to pass data through.
// create the Manchester driver and provide the BPS (bits per second)
driver := manchester.NewManchesterDriver(*bps)
// create the data frame
frame := manchester.BuildDataFrame([]byte(*text))
// open the pin on GPIO using your favorite library
pin, _ := gpio.OpenPin(*senderPin, gpio.ModeOutput)
defer pin.Close()
// the writer function will be called by the driver to set on/off state
// for the pin
writer := func(level bool) {
if level {
pin.Set()
} else {
pin.Clear()
}
}
// this is the set of impulses to reduce the noise
for i := 1; i < 50; i++ {
pin.Set()
driver.Sleep()
pin.Clear()
driver.Sleep()
}
// write the frame down the stream
frame.WriteFrame(func(bit bool) {
driver.WriteBit(bit, writer)
})
This is slightly more complicated, because we expect a lot of noise in the surrounding EM field.
func receive(bps int64, pinNum int) {
pin, err := gpio.OpenPin(pinNum, gpio.ModeInput)
if err != nil {
panic(err)
}
// create the resulting frame
frame := manchester.NewDataFrame()
// create the driver
driver := manchester.NewManchesterDriver(bps)
// this structure is used to decouple the pin processing from the syscall watch.
type Event struct {
pinState bool
eventTime int64
}
// the receiver channel for the events from the pin
events := make(chan Event, 1000)
var latch sync.WaitGroup
latch.Add(1)
// the main loop to handle the events from the channel as they are reported by the watcher
go func() {
worker := func(evt Event) {
var state manchester.Edge
if evt.pinState {
state = manchester.Up
} else {
state = manchester.Down
}
driver.ReadBit(state, evt.eventTime, func(x bool) {
if frame.ReadBit(x) { // here it will return true if the frame was read completely.
if frame.IsValid() {
fmt.Println("============================")
fmt.Println(string(frame.Data))
latch.Done()
} else {
// if the chechsum does not match - then the frame was corrupted on the way.
fmt.Println("Missed")
// reset the internal frame structures
frame.Reset()
}
}
})
}
for {
worker(<-events)
}
}()
// watch the events on the pin via syscall.
if err = pin.BeginWatch(gpio.EdgeBoth, func() {
received := time.Now().UnixNano()
events <- Event{pin.Get(), received}
}); err != nil {
panic(err)
}
defer pin.EndWatch()
defer pin.Close()
latch.Wait()
}