Initial support for rfm69 radio

controller/doc.go

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+// Package controller is a container for the various device controllers supported by EMBD.
+package controller

radio/doc.go

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+package radio

radio/rfm69/README.md

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+RFM69 Driver Info
+=================
+
+
+
+Interesting links
+-----------------
+- Info about listen mode with low duty cycle: https://lowpowerlab.com/forum/low-power-techniques/ultra-low-power-listening-mode-for-battery-nodes/

radio/rfm69/registers.go

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+// Copyright 2016 by Thorsten von Eicken
+
+package rfm69
+
+const (
+	REG_FIFO       = 0x00
+	REG_OPMODE     = 0x01
+	REG_FRFMSB     = 0x07
+	REG_PALEVEL    = 0x11
+	REG_LNAVALUE   = 0x18
+	REG_AFCMSB     = 0x1F
+	REG_AFCLSB     = 0x20
+	REG_FEIMSB     = 0x21
+	REG_FEILSB     = 0x22
+	REG_RSSIVALUE  = 0x24
+	REG_IRQFLAGS1  = 0x27
+	REG_IRQFLAGS2  = 0x28
+	REG_SYNCVALUE1 = 0x2F
+	REG_SYNCVALUE2 = 0x30
+	REG_NODEADDR   = 0x39
+	REG_BCASTADDR  = 0x3A
+	REG_FIFOTHRESH = 0x3C
+	REG_PKTCONFIG2 = 0x3D
+	REG_AESKEYMSB  = 0x3E
+
+	MODE_SLEEP    = 0 << 2
+	MODE_STANDBY  = 1 << 2
+	MODE_TRANSMIT = 3 << 2
+	MODE_RECEIVE  = 4 << 2
+
+	START_TX = 0xC2
+	STOP_TX  = 0x42
+
+	RCCALSTART        = 0x80
+	IRQ1_MODEREADY    = 1 << 7
+	IRQ1_RXREADY      = 1 << 6
+	IRQ1_SYNADDRMATCH = 1 << 0
+
+	IRQ2_FIFONOTEMPTY = 1 << 6
+	IRQ2_PACKETSENT   = 1 << 3
+	IRQ2_PAYLOADREADY = 1 << 2
+)
+
+// register values to initialize the chip, this array has pairs of <address, data>
+var configRegs = []byte{
+	// POR value is better for first rf_sleep  0x01, 0x00, // OpMode = sleep
+	0x02, 0x00, // DataModul = packet mode, fsk
+	0x03, 0x02, // BitRateMsb, data rate = 49,261 khz
+	0x04, 0x8A, // BitRateLsb, divider = 32 MHz / 650
+	0x05, 0x02, // FdevMsb = 45 KHz
+	0x06, 0xE1, // FdevLsb = 45 KHz
+	0x0B, 0x20, // Low M
+	0x19, 0x4A, // RxBw 100 KHz
+	0x1A, 0x42, // AfcBw 125 KHz
+	0x1E, 0x0C, // AfcAutoclearOn, AfcAutoOn
+	//0x25, 0x40, //0x80, // DioMapping1 = SyncAddress (Rx)
+	0x26, 0x07, // disable clkout
+	0x29, 0xA0, // RssiThresh -80 dB
+	0x2D, 0x05, // PreambleSize = 5
+	0x2E, 0x88, // SyncConfig = sync on, sync size = 2
+	0x2F, 0x2D, // SyncValue1 = 0x2D
+	0x37, 0xD0, // PacketConfig1 = fixed, white, no filtering
+	0x38, 0x42, // PayloadLength = 0, unlimited
+	0x3C, 0x8F, // FifoTresh, not empty, level 15
+	0x3D, 0x12, // 0x10, // PacketConfig2, interpkt = 1, autorxrestart off
+	0x6F, 0x20, // TestDagc ...
+	0x71, 0x02, // RegTestAfc
+}

radio/rfm69/rfm69.go

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+// Copyright 2016 by Thorsten von Eicken
+
+// The RFM69 package interfaces with a HopeRF RFM69 radio connected to an SPI bus. In addition,
+// an interrupt capable GPIO pin may be used to avoid having to poll the radio.
+package rfm69
+
+import (
+	"fmt"
+	"log"
+
+	"github.com/kidoman/embd"
+)
+
+// rfm69 represents a HopeRF RFM69 radio
+type rfm69 struct {
+	// configuration
+	spi     embd.SPIBus       // bus where the radio is connected
+	intrPin embd.InterruptPin // interrupt pin for RX and TX interrupts
+	id      byte              // my RF ID/address
+	group   byte              // RF address of group
+	freq    int               // center frequency
+	parity  byte              // ???
+	// state
+	mode byte // current operation mode
+	// info about current RX packet
+	rxInfo *RxInfo
+}
+
+type Packet struct {
+	Length  uint8 // number of message bytes plus 1 for the address byte
+	Address uint8 // destination address
+	Message []byte
+}
+
+type RxInfo struct {
+	rssi int // rssi value for current packet
+	lna  int // low noise amp gain for current packet
+	fei  int // frequency error for current packet
+	afc  int // frequency correction applied for current packet
+}
+
+// New creates a connection to an rfm69 radio connected to the provided SPI bus and interrupt pin.
+// the bufCount determines how many transmit buffers are allocated to allow for the queueing of
+// transmit packets.
+// For the RFM69 the SPI bus must be set to 10Mhz and mode 0.
+func New(bus embd.SPIBus, intr embd.InterruptPin, id, group byte, freq int) *rfm69 {
+	// bit 7 = b7^b5^b3^b1; bit 6 = b6^b4^b2^b0
+	parity := group ^ (group << 4)
+	parity = (parity ^ (parity << 2)) & 0xc0
+	return &rfm69{spi: bus, intrPin: intr, id: id, group: group, freq: freq, parity: parity,
+		mode: 255}
+}
+
+func (rf *rfm69) writeReg(addr, data byte) error {
+	buf := []byte{addr | 0x80, data}
+	return rf.spi.TransferAndReceiveData(buf)
+}
+
+func (rf *rfm69) readReg(addr byte) (byte, error) {
+	buf := []byte{addr & 0x7f, 0}
+	err := rf.spi.TransferAndReceiveData(buf)
+	return buf[1], err
+}
+
+func (rf *rfm69) Init() error {
+	// try to establish communication with the rfm69
+	sync := func(pattern byte) error {
+		n := 10
+		for {
+			rf.writeReg(REG_SYNCVALUE1, pattern)
+			v, err := rf.readReg(REG_SYNCVALUE1)
+			if err != nil {
+				return err
+			}
+			if v == pattern {
+				return nil
+			}
+			if n == 0 {
+				return fmt.Errorf("Cannot sync with rfm69 chip")
+			}
+			n--
+		}
+	}
+	if err := sync(0xaa); err != nil {
+		return err
+	}
+	if err := sync(0x55); err != nil {
+		return err
+	}
+
+	// write the configuration into the registers
+	for i := 0; i < len(configRegs)-1; i += 2 {
+		if err := rf.writeReg(configRegs[i], configRegs[i+1]); err != nil {
+			return err
+		}
+	}
+
+	rf.setFrequency(rf.freq)
+	rf.writeReg(REG_SYNCVALUE2, rf.group)
+
+	if gpio, ok := rf.intrPin.(embd.DigitalPin); ok {
+		log.Printf("Set intr direction")
+		gpio.SetDirection(embd.In)
+	}
+	if err := rf.intrPin.Watch(embd.EdgeRising, rf.intrHandler); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (rf *rfm69) setFrequency(freq int) {
+	// accept any frequency scale as input, including KHz and MHz
+	// multiply by 10 until freq >= 100 MHz
+	for freq > 0 && freq < 100000000 {
+		freq = freq * 10
+	}
+
+	// Frequency steps are in units of (32,000,000 >> 19) = 61.03515625 Hz
+	// use multiples of 64 to avoid multi-precision arithmetic, i.e. 3906.25 Hz
+	// due to this, the lower 6 bits of the calculated factor will always be 0
+	// this is still 4 ppm, i.e. well below the radio's 32 MHz crystal accuracy
+	// 868.0 MHz = 0xD90000, 868.3 MHz = 0xD91300, 915.0 MHz = 0xE4C000
+	frf := (freq << 2) / (32000000 >> 11)
+	rf.writeReg(REG_FRFMSB, byte(frf>>10))
+	rf.writeReg(REG_FRFMSB+1, byte(frf>>2))
+	rf.writeReg(REG_FRFMSB+2, byte(frf<<6))
+}
+
+func (rf *rfm69) setMode(mode byte) error {
+	reg, err := rf.readReg(REG_OPMODE)
+	if err != nil {
+		return err
+	}
+	reg = (reg & 0xE3) | mode
+	err = rf.writeReg(REG_OPMODE, reg)
+	if err != nil {
+		return err
+	}
+	for {
+		val, err := rf.readReg(REG_IRQFLAGS1)
+		if err != nil {
+			rf.mode = 255
+			return err
+		}
+		if val&IRQ1_MODEREADY != 0 {
+			rf.mode = mode
+			return nil
+		}
+	}
+}
+
+func (rf *rfm69) Send(header byte, message []byte) error {
+	if len(message) > 62 {
+		return fmt.Errorf("message too long")
+	}
+	rf.setMode(MODE_SLEEP)
+
+	buf := make([]byte, len(message)+4)
+	buf[0] = REG_FIFO | 0x80
+	buf[1] = byte(len(message) + 2)
+	buf[2] = (header & 0x3f) | rf.parity
+	buf[3] = (header & 0xC0) | rf.id
+	copy(buf[4:], message)
+	err := rf.spi.TransferAndReceiveData(buf)
+	if err != nil {
+		return err
+	}
+	rf.setMode(MODE_TRANSMIT)
+	for {
+		val, err := rf.readReg(REG_IRQFLAGS2)
+		if err != nil {
+			return err
+		}
+		if val&IRQ2_PACKETSENT != 0 {
+			break
+		}
+	}
+	rf.setMode(MODE_STANDBY)
+	return nil
+}
+
+func (rf *rfm69) readInfo() *RxInfo {
+	// collect rxinfo, start with rssi
+	rxInfo := &RxInfo{}
+	rssi, _ := rf.readReg(REG_RSSIVALUE)
+	rxInfo.rssi = 0 - int(rssi)/2
+	// low noise amp gain
+	lna, _ := rf.readReg(REG_LNAVALUE)
+	rxInfo.lna = int((lna >> 3) & 0x7)
+	// auto freq correction applied, caution: signed value
+	buf := []byte{REG_AFCMSB, 0, 0}
+	rf.spi.TransferAndReceiveData(buf)
+	rxInfo.afc = int(int8(buf[1]))<<8 | int(buf[2])
+	// freq error detected, caution: signed value
+	buf = []byte{REG_FEIMSB, 0, 0}
+	rf.spi.TransferAndReceiveData(buf)
+	rxInfo.fei = int(int8(buf[1]))<<8 | int(buf[2])
+	return rxInfo
+}
+
+func (rf *rfm69) Receive() (header byte, message []byte, info *RxInfo, err error) {
+	// if we're not in receive mode, then switch, this also flushes the FIFO
+	if rf.mode != MODE_RECEIVE {
+		rf.setMode(MODE_RECEIVE)
+		return
+	}
+
+	// if we don't have rxinfo check whether we have RX_READY, which means that we've
+	// started receiving a packet so we can collect info
+	if rf.rxInfo == nil {
+		irq1, err := rf.readReg(REG_IRQFLAGS1)
+		if err != nil {
+			return 0, nil, nil, err
+		}
+		if irq1&IRQ1_RXREADY != 0 {
+			rf.rxInfo = rf.readInfo()
+		}
+	}
+
+	// see whether we have a full packet
+	irq2, err := rf.readReg(REG_IRQFLAGS2)
+	if err != nil {
+		return 0, nil, nil, err
+	}
+	if irq2&IRQ2_PAYLOADREADY == 0 {
+		return
+	}
+	i2 := rf.readInfo()
+	if rf.rxInfo != nil && i2 != nil &&
+		(rf.rxInfo.rssi != i2.rssi || rf.rxInfo.lna != i2.lna ||
+			rf.rxInfo.afc != i2.afc || rf.rxInfo.fei != i2.fei) {
+		fmt.Printf("\nrxInfo mismatch: %+v vs %+v\n", *rf.rxInfo, *i2)
+	}
+	// got packet, read it by fetching the entire FIFO, should be faster than first
+	// looking at the length
+	buf := make([]byte, 67)
+	buf[0] = REG_FIFO
+	err = rf.spi.TransferAndReceiveData(buf)
+	if err != nil {
+		return 0, nil, nil, err
+	}
+	// return the packet
+	info = rf.rxInfo
+	rf.rxInfo = nil
+	l := buf[1]
+	if l > 66 {
+		l = 66 // or error?
+	}
+	header = buf[2]
+	message = buf[3 : 2+l]
+	return
+}
+
+func (rf *rfm69) intrHandler(pin embd.DigitalPin) {
+	log.Printf("Interrupt called!")
+}