SX1278 OOK waveform view with C# chart control

Dragino Lora Shield (Semtech SX1278)
Arduino Due
Visual Studio, C#

Arduino code

#include <SPI.h>

#define SERIAL_SPEED        57600
#define BPS                 1200
#define FREQ                433.9855
#define STATE_SLEEP         0
#define STATE_STANDBY       1
#define STATE_FSRX          4
#define STATE_RX            5
#define S_DELAY             10
#define L_DELAY             100

#define CH_FILTER_BW B00001100 // 25 kHz

#define DCLK_PIN 6
#define DATA_PIN 7

#define RegOpMode           0x01
#define RegBitrateMsb       0x02
#define RegBitrateLsb       0x03
#define RegFrfMsb           0x06
#define RegFrfMid           0x07
#define RegFrfLsb           0x08
#define RegPaRamp           0x0a
#define RegRssiConfig       0x0e
#define RegRssiValue        0x11
#define RegRxBw             0x12
#define RegOokPeak          0x14
#define RegPreambleDetect   0x1f
#define RegSyncConfig       0x27
#define RegPacketConfig1    0x30
#define RegPacketConfig2    0x31
#define RegIrqFlags2        0x3f
#define RegDioMapping1      0x40
#define RegVersion          0x42

#define SX_OSC_FREQ         32000000
#define SX_RESET            9
#define SX_RESET_DELAY_H    5
#define SX_RESET_DELAY_L    100
#define SPI_SS              10
#define SPI_RW_DELAY        50

volatile uint32_t duration = 0;
volatile bool chg = false;

void setup() {
Serial.begin(SERIAL_SPEED);
if (initSX()) {
    pinMode(DATA_PIN, INPUT);
    pinMode(DCLK_PIN, INPUT);
    delay(S_DELAY);
    startFSK();
    // OOK
    uint8_t b = readSPI(RegOpMode);
    bitClear(b, 6);
    bitSet(b, 5);
    writeSPI(RegOpMode, b);

// Channel filter bandwidth control
writeSPI(RegRxBw, CH_FILTER_BW);

setFreq(FREQ);
setBps(BPS);

    // Bits 7-6: AutoRestartRxMode, 01  On, without waiting for the PLL to re-lock
    // Bit 4: Enables the Sync word generation and detection: 0 => Off, 1 => On
    // Bit 5: Sets the polarity of the Preamble. 0  0xAA, 1  0x55
    // Bits 2-0: Size of the Sync word (SyncSize + 1)
    b = readSPI(RegSyncConfig);
    bitClear(b, 7);
    bitSet(b, 6);
    bitClear(b, 4);
    bitClear(b, 5);
    writeSPI(RegSyncConfig, b);

    // Bits 6-5: Defines DC-free encoding/decoding performed: 00->none, 01->manchester, 10->whitening
    // Bit 7: packet format, 0 = fixed length, 1 = variable length
    // Bit 4: crc calc/check, 0 = off, 1 = on
    // Bits 2-1: Defines address based filtering in Rx: 00 ïƒ None (Off)
    // Bit 3: Defines the behavior of the packet handler when CRC check fails:
    // 0 => Clear FIFO and restart new packet reception. No PayloadReady interrupt issued.
    // 1 => Do not clear FIFO. PayloadReady interrupt issued.
    // Bit 0: Selects the CRC and whitening algorithms:
    // 0  CCITT CRC implementation with standard whitening
    // 1  IBM CRC implementation with alternate whitening
    b = 0;
    bitSet(b, 7);
    writeSPI(RegPacketConfig1, b);

    // Bits 6-5: FSK data shaping:
    // 00 -> no shaping, 01 -> Gaussian filter BT = 1.0
    // 10 -> Gaussian filter BT = 0.5, 11 -> Gaussian filter BT = 0.3
    // Bits 3-0: Rise/Fall time of ramp up/down in FSK:
    // 1001  40 us
    b = readSPI(RegPaRamp);
    bitClear(b, 6);
    bitClear(b, 5);
    bitSet(b, 3);
    bitClear(b, 2);
    bitClear(b, 1);
    bitSet(b, 0);
    writeSPI(RegPaRamp, b);

    // Data processing mode: 0 => Continuous mode, 1 => Packet mode
    b = readSPI(RegPacketConfig2);
    bitClear(b, 6);
    writeSPI(RegPacketConfig2, b);

    // Set DIO mapping
    b = readSPI(RegDioMapping1);
    bitClear(b, 5);
    bitClear(b, 4);
    bitClear(b, 3);
    bitClear(b, 2);
    writeSPI(RegDioMapping1, b);

    // RSSI smoothing.
    // Defines the number of samples taken to average the RSSI result. 000 -> 2 samples
    b = readSPI(RegRssiConfig);
    bitClear(b, 2);
    bitClear(b, 1);
    bitClear(b, 0);
    writeSPI(RegRssiConfig, b);

    // Bit 5: enables the Bit Synchronizer:
    // 0 -> bit sync disabled (not possible in packet mode), 1 -> bit sync enabled
    b = readSPI(RegOokPeak);
    bitClear(b, 5);
    writeSPI(RegOokPeak, b);

    // RegPreambleDetect (0x1f). Enables Preamble detector when set to 1.
    // The AGC settings supersede this bit during the startup / AGC phase.
    // Bit 7: 0 -> turned off, 1 -> turned on
    // Bits 6-5: Number of Preamble bytes to detect to trigger an interrupt.
    // 00  1 byte, 10  3 bytes, 01  2 bytes
    b = readSPI(RegPreambleDetect);
    bitClear(b, 7);
    writeSPI(RegPreambleDetect, b);

clearFifoAndFlags();

    digitalWrite(DCLK_PIN, LOW);
    digitalWrite(DATA_PIN, LOW);
    attachInterrupt(digitalPinToInterrupt(DATA_PIN), isr, CHANGE);

    setState(STATE_FSRX);
    delay(L_DELAY);
    setState(STATE_RX);
//    delay(S_DELAY);
}
}

void loop() {
if (chg) {
chg = false;
Serial.println(duration);
}
}

void isr() {
static uint32_t lastTi = 0;

uint32_t ti = micros();
duration = ti - lastTi;
chg = true;
lastTi = ti;
}

void clearFifoAndFlags() {
// Flag(s) and FIFO are cleared when this bit is set
uint8_t b = readSPI(RegIrqFlags2);
bitSet(b, 4);
writeSPI(RegIrqFlags2, b);
delay(S_DELAY);
}

void setBps(uint16_t bps) {
uint16_t baudRate = SX_OSC_FREQ / bps;
writeSPI(RegBitrateMsb, baudRate >> 8);
writeSPI(RegBitrateLsb, baudRate & 0xff);
}

void setFreq(float f)
{
uint32_t lf = (f * 1000000) / 61.035;
writeSPI(RegFrfMsb, (lf >> 16) & 0xff);
writeSPI(RegFrfMid, (lf >> 8) & 0xff);
writeSPI(RegFrfLsb, lf & 0xff);
}

void setState(uint8_t s) {
uint8_t b = readSPI(RegOpMode);
b = b | s;
writeSPI(RegOpMode, b);
}

void startFSK()
{
setState(STATE_SLEEP);
delay(S_DELAY);
uint8_t b = readSPI(RegOpMode);
bitClear(b, 7);
writeSPI(RegOpMode, b);
}

bool initSX() {
pinMode(SX_RESET, OUTPUT);
resetSX();
initSPI();
if (readSPI(RegVersion) == 0) {
return false;
}
setState(STATE_STANDBY);
return true;
}

void resetSX() {
digitalWrite(SX_RESET, LOW);
delayMicroseconds(SX_RESET_DELAY_L);
digitalWrite(SX_RESET, HIGH);
delay(SX_RESET_DELAY_H);
}

uint8_t readSPI(uint8_t addr) {
digitalWrite(SPI_SS, LOW);
SPI.transfer(addr);
delayMicroseconds(SPI_RW_DELAY);
uint8_t v = SPI.transfer(0x00);
digitalWrite(SPI_SS, HIGH);
return v;
}

void writeSPI(uint8_t addr, uint8_t v) {
digitalWrite(SPI_SS, LOW);
SPI.transfer(addr | 0x80);
delayMicroseconds(SPI_RW_DELAY);
SPI.transfer(v);
digitalWrite(SPI_SS, HIGH);
}

void initSPI()
{
digitalWrite(SPI_SS, HIGH);
pinMode(SPI_SS, OUTPUT);
SPI.begin();
SPI.setDataMode(SPI_MODE0);
SPI.setBitOrder(MSBFIRST);
}

C# code

using System;
using System.Collections;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.IO.Ports;

namespace SxWavePlot
{
    public partial class FormMain : Form
    {
        private bool _run = false;
        private ArrayList _xValues = new ArrayList();
        private int _val = 1;
        public FormMain()
        {
            InitializeComponent();
            ListSerialPorts();
        }

        private void buttonStart_Click(object sender, EventArgs e)
        {
            if (!serialPort1.IsOpen)
            {
                serialPort1.PortName = comboBoxComPorts.GetItemText(comboBoxComPorts.SelectedItem);
                serialPort1.BaudRate = 57600;
                try
                {
                    serialPort1.Open();
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message, "SxWavePlot", MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                    return;
                }
                _val = 1;
                chart1.Series[0].Points.Clear();
                buttonStart.Enabled = false;
                comboBoxComPorts.Enabled = false;
                buttonListPorts.Enabled = false;
                buttonStop.Enabled = true;
                _run = true;
            }
        }

        private void serialPort1_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
        {
            if (_run)
            {
                string s = serialPort1.ReadLine();
                int v;
                if (Int32.TryParse(s, out v))
                {
                    v = (int)(v / 100);
                    for (int i = 0; i < v; i++)
                    {
                        _xValues.Add(_val);
                    }
                    _val = 1 - _val;
                }
            }
        }

        private void ListSerialPorts()
        {
            buttonStart.Enabled = false;
            comboBoxComPorts.Items.Clear();
            string[] ports = SerialPort.GetPortNames();
            Array.Sort(ports);
            foreach (string port in ports)
            {
                comboBoxComPorts.Items.Add(port);
            }
            if (ports.Length > 0)
            {
                buttonStart.Enabled = true;
            }
        }

        private void buttonStop_Click(object sender, EventArgs e)
        {
            _run = false;
            chart1.Series[0].Points.DataBindY(_xValues);
            _xValues.Clear();
            Task.Run(() =>
            {
                try
                {
                    serialPort1.Close();
                }
                catch { }
            });
            buttonStop.Enabled = false;
            comboBoxComPorts.Enabled = true;
            buttonListPorts.Enabled = true;
            buttonStart.Enabled = true;
        }