/
low_level.go
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/
low_level.go
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// Copyright 2018 The Periph Authors. All rights reserved.
// Use of this source code is governed under the Apache License, Version 2.0
// that can be found in the LICENSE file.
package commands
import (
"fmt"
"time"
"periph.io/x/conn/v3/gpio"
"periph.io/x/conn/v3/physic"
"periph.io/x/conn/v3/spi"
)
// Card authentication status enum.
const (
AuthOk AuthStatus = iota
AuthReadFailure
AuthFailure
)
// LowLevel is a low-level handler of a MFRC522 RFID reader.
type LowLevel struct {
resetPin gpio.PinOut
irqPin gpio.PinIn
spiDev spi.Conn
antennaGain int
stop chan struct{}
}
// AuthStatus indicates the authentication response, could be one of AuthOk,
// AuthReadFailure or AuthFailure
type AuthStatus byte
// NewLowLevelSPI creates and initializes the RFID card reader attached to SPI.
//
// spiPort - the SPI device to use.
// resetPin - reset GPIO pin.
// irqPin - irq GPIO pin.
func NewLowLevelSPI(spiPort spi.Port, resetPin gpio.PinOut, irqPin gpio.PinIn) (*LowLevel, error) {
if resetPin == nil {
return nil, wrapf("reset pin is not set")
}
spiDev, err := spiPort.Connect(10*physic.MegaHertz, spi.Mode0, 8)
if err != nil {
return nil, err
}
if err := resetPin.Out(gpio.High); err != nil {
return nil, err
}
if irqPin != nil {
if err := irqPin.In(gpio.PullUp, gpio.FallingEdge); err != nil {
return nil, err
}
}
dev := &LowLevel{
spiDev: spiDev,
irqPin: irqPin,
resetPin: resetPin,
antennaGain: 4,
stop: make(chan struct{}, 1),
}
return dev, nil
}
// Reset resets the RFID chip to initial state.
func (r *LowLevel) Reset() error {
return r.DevWrite(CommandReg, PCD_RESETPHASE)
}
// SetAntennaGain sets the antenna gain for the driver.
// This method does not update the gain on the device itself.
// A subsequent call to SetAntenna is necessary to have an effect.
func (r *LowLevel) SetAntennaGain(gain int) {
r.antennaGain = gain
}
// Init initializes the RFID chip.
func (r *LowLevel) Init() error {
if err := r.Reset(); err != nil {
return err
}
if err := r.writeCommandSequence(sequenceCommands.init); err != nil {
return err
}
gain := byte(r.antennaGain) << 4
if err := r.DevWrite(int(RFCfgReg), gain); err != nil {
return err
}
return r.SetAntenna(true)
}
// SetAntenna configures the antenna state, on/off.
func (r *LowLevel) SetAntenna(state bool) error {
if state {
current, err := r.DevRead(TxControlReg)
if err != nil {
return err
}
if current&0x03 != 0 {
return wrapf("can not set the bitmask for antenna")
}
return r.SetBitmask(TxControlReg, 0x03)
}
return r.ClearBitmask(TxControlReg, 0x03)
}
// String implements conn.Resource.
func (r *LowLevel) String() string {
return fmt.Sprintf("Mifare MFRC522 [bus: %v, reset pin: %s, irq pin: %s]",
r.spiDev, r.resetPin.Name(), r.irqPin.Name())
}
// DevWrite sends data to a device.
func (r *LowLevel) DevWrite(address int, data byte) error {
newData := []byte{(byte(address) << 1) & 0x7E, data}
return r.spiDev.Tx(newData, nil)
}
// DevRead gets data from a device.
func (r *LowLevel) DevRead(address int) (byte, error) {
data := []byte{((byte(address) << 1) & 0x7E) | 0x80, 0}
out := make([]byte, len(data))
if err := r.spiDev.Tx(data, out); err != nil {
return 0, err
}
return out[1], nil
}
// CRC calculates the CRC of the data using the card chip.
func (r *LowLevel) CRC(inData []byte) ([]byte, error) {
if err := r.ClearBitmask(DivIrqReg, 0x04); err != nil {
return nil, err
}
if err := r.SetBitmask(FIFOLevelReg, 0x80); err != nil {
return nil, err
}
for _, v := range inData {
if err := r.DevWrite(FIFODataReg, v); err != nil {
return nil, err
}
}
if err := r.DevWrite(CommandReg, PCD_CALCCRC); err != nil {
return nil, err
}
for i := byte(0xFF); i > 0; i-- {
n, err := r.DevRead(DivIrqReg)
if err != nil {
return nil, err
}
if n&0x04 > 0 {
break
}
}
lsb, err := r.DevRead(CRCResultRegL)
if err != nil {
return nil, err
}
msb, err := r.DevRead(CRCResultRegM)
if err != nil {
return nil, err
}
return []byte{lsb, msb}, nil
}
// SetBitmask sets register bit.
func (r *LowLevel) SetBitmask(address, mask int) error {
current, err := r.DevRead(address)
if err != nil {
return err
}
return r.DevWrite(address, current|byte(mask))
}
// ClearBitmask clears register bit.
func (r *LowLevel) ClearBitmask(address, mask int) error {
current, err := r.DevRead(address)
if err != nil {
return err
}
return r.DevWrite(address, current&^byte(mask))
}
// StopCrypto stops the crypto chip.
func (r *LowLevel) StopCrypto() error {
return r.ClearBitmask(Status2Reg, 0x08)
}
// WaitForEdge waits for an IRQ pin to strobe. If IRQ pin is not set, then always returns false immediately.
func (r *LowLevel) WaitForEdge(timeout time.Duration) error {
irqChannel := make(chan bool)
go func() {
defer close(irqChannel)
irqChannel <- r.irqPin.WaitForEdge(timeout)
}()
if err := r.Init(); err != nil {
return err
}
if err := r.writeCommandSequence(sequenceCommands.waitInit); err != nil {
return err
}
for {
if err := r.writeCommandSequence(sequenceCommands.waitLoop); err != nil {
return err
}
select {
case <-r.stop:
return wrapf("halt")
case irqResult := <-irqChannel:
if !irqResult {
return wrapf("timeout waiting for IRQ edge: %v", timeout)
}
return nil
case <-time.After(100 * time.Millisecond):
// do nothing
}
}
}
// ClearInterrupt removes any pending host interrupts
func (r *LowLevel) ClearInterrupt() {
r.irqPin.WaitForEdge(0)
}
// Auth authenticate the card fof the sector/block using the provided data.
//
// mode - the authentication mode.
// sector - the sector to authenticate on.
// block - the block within sector to authenticate.
// sectorKey - the key to be used for accessing the sector data.
// serial - the serial of the card.
func (r *LowLevel) Auth(mode byte, blockAddress byte, sectorKey [6]byte, serial []byte) (AuthStatus, error) {
buffer := make([]byte, 2)
buffer[0] = mode
buffer[1] = blockAddress
buffer = append(buffer, sectorKey[:]...)
buffer = append(buffer, serial[:4]...)
_, _, err := r.CardWrite(PCD_AUTHENT, buffer)
if err != nil {
return AuthReadFailure, err
}
if n, err := r.DevRead(Status2Reg); err != nil || n&0x08 == 0 {
return AuthFailure, err
}
return AuthOk, nil
}
// CardWrite the low-level interface to write some raw commands to the card.
//
// command - the command register
// data - the data to write out to the card using the authenticated sector.
func (r *LowLevel) CardWrite(command byte, data []byte) ([]byte, int, error) {
var backData []byte
backLength := -1
irqEn := byte(0x00)
irqWait := byte(0x00)
switch command {
case PCD_AUTHENT:
irqEn = 0x12
irqWait = 0x10
case PCD_TRANSCEIVE:
irqEn = 0x77
irqWait = 0x30
}
if err := r.DevWrite(CommIEnReg, irqEn|0x80); err != nil {
return nil, -1, err
}
if err := r.ClearBitmask(CommIrqReg, 0x80); err != nil {
return nil, -1, err
}
if err := r.SetBitmask(FIFOLevelReg, 0x80); err != nil {
return nil, -1, err
}
if err := r.DevWrite(CommandReg, PCD_IDLE); err != nil {
return nil, -1, err
}
for _, v := range data {
if err := r.DevWrite(FIFODataReg, v); err != nil {
return nil, -1, err
}
}
if err := r.DevWrite(CommandReg, command); err != nil {
return nil, -1, err
}
if command == PCD_TRANSCEIVE {
if err := r.SetBitmask(BitFramingReg, 0x80); err != nil {
return nil, -1, err
}
}
i := 2000
n := byte(0)
for ; i > 0; i-- {
var err error
if n, err = r.DevRead(CommIrqReg); err != nil {
return nil, -1, err
}
if n&(irqWait|1) != 0 {
break
}
}
if err := r.ClearBitmask(BitFramingReg, 0x80); err != nil {
return nil, -1, err
}
if i == 0 {
return nil, -1, wrapf("can't read data after 2000 loops")
}
if d, err := r.DevRead(ErrorReg); err != nil || d&0x1B != 0 {
return nil, -1, err
}
if n&irqEn&0x01 == 1 {
return nil, -1, wrapf("IRQ error")
}
if command == PCD_TRANSCEIVE {
n, err := r.DevRead(FIFOLevelReg)
if err != nil {
return nil, -1, err
}
lastBits, err := r.DevRead(ControlReg)
if err != nil {
return nil, -1, err
}
lastBits = lastBits & 0x07
if lastBits != 0 {
backLength = (int(n)-1)*8 + int(lastBits)
} else {
backLength = int(n) * 8
}
if n == 0 {
n = 1
}
if n > 16 {
n = 16
}
backData = make([]byte, n)
for i := byte(0); i < n; i++ {
byteVal, err := r.DevRead(FIFODataReg)
if err != nil {
return nil, -1, err
}
backData[i] = byteVal
}
}
return backData, backLength, nil
}
// Halt stops the card and cleans up resources.
func (r *LowLevel) Halt() error {
close(r.stop)
return r.DevWrite(CommandReg, 16)
}
func (r *LowLevel) writeCommandSequence(commands [][]byte) error {
for _, cmdData := range commands {
if err := r.DevWrite(int(cmdData[0]), cmdData[1]); err != nil {
return err
}
}
return nil
}
func wrapf(format string, a ...interface{}) error {
return fmt.Errorf("mfrc522 lowlevel: "+format, a...)
}
// the command batches for card init and wait loop.
var sequenceCommands = struct {
init [][]byte
waitInit [][]byte
waitLoop [][]byte
}{
init: [][]byte{
{TModeReg, 0x8D},
{TPrescalerReg, 0x3E},
{TReloadRegL, 30},
{TReloadRegH, 0},
{TxAutoReg, 0x40},
{ModeReg, 0x3D},
},
waitInit: [][]byte{
{CommIrqReg, 0x00},
{CommIEnReg, 0xA0},
},
waitLoop: [][]byte{
{FIFODataReg, 0x26},
{CommandReg, 0x0C},
{BitFramingReg, 0x87},
},
}