GDG DevFest Minneapolis - How to write your own custom driver for Android Things

Speaker slides of the How to write your own custom driver for Android Things done at the GDG DevFest Minneapolis

Transcript

1. James Coggan How to write your own custom driver for Android Things https://jamescoggan.com @mad_team
2. What is Android Things?
3. What is the goal?
4. Hey Google, Turn the kettle on
6. Hey Google, turn the fan on
7. Smart fan?
9. Wireless Remote Control Sockets ! Pros ◦ 433 MHz (~30m range) ◦ Cheap (6 for $25) ◦ No need for central hub ! Cons ◦ No security ◦ Not connected (needs remote)
10. First of all, how do they work?
11. Encoder/Decoder
12. Radio wave
13. Zero
14. One
18. How to connect the socket to Android Things?
19. $3.00
20. Wireless Remote Control Sockets ! Receiver ◦ 5 volts ! Transmitter ◦ 3 to 12 volts ◦ 20 to 200 meters (depends on voltage)
21. Raspberry Pi Receiver Transmitter
22. Raspberry Pi Receiver Transmitter 5v Ground
23. Raspberry Pi Receiver Transmitter 5v Ground
24. ! Raspberry PI ◦ Provides 5V ◦ IO pins are 3.3v ! Receiver signal is 5v instead of 3.3v ◦ We need a voltage divider
25. Raspberry Pi Receiver Transmitter 5v Ground
26. Raspberry Pi Receiver Transmitter 5v Ground
27. Supported I/Os ! General Purpose Input/Output (GPIO): Binary ! Universal Asynchronous Receiver Transmitter (UART) ! Inter-Integrated Circuit(I2C) ! Pulse Width Modulation (PWM): Servo motors, DC motors ! Serial Peripheral Interface (SPI)
28. class RCReceiver : AutoCloseable{ private val gpio: Gpio override fun close() { gpio.close() } }
29. class RCReceiver(val portName: String) : AutoCloseable{ private val gpio: Gpio init { gpio = PeripheralManagerService().openGpio(portName) gpio.setDirection(Gpio.DIRECTION_IN) gpio.setEdgeTriggerType(Gpio.EDGE_BOTH) gpio.setActiveType(Gpio.ACTIVE_HIGH) } override fun close() { gpio.close() } }
30. gpio.registerGpioCallback(object : GpioCallback() { override fun onGpioEdge(gpio: Gpio?): Boolean { return true } })
31. gpio.registerGpioCallback(object : GpioCallback() { override fun onGpioEdge(gpio: Gpio?): Boolean { onGpioSwitch() return true } })
32. private var separationLimit = 4300 // In micros private var lastTime = 0L private var startOfData = false private var timings = LongArray(20)
33. private fun onGpioSwitch() { val time = (System.nanoTime() / 1000) // Micros val duration = time - lastTime timings[changeCount++] = duration lastTime = time }
34. private fun onGpioSwitch() { … if (duration > separationLimit) { // block ended } }
35. if (duration > separationLimit) { if (startOfData) { val codeInBinaryString = processData(changeCount) codeInBinaryString?.let { onResultListener.onResult(codeInBinaryString) } startOfData = false } else { startOfData = true } changeCount = 0 }
36. private var code = 0L class HighLow(val high: Int, // High pulse duration val low: Int. // Low pulse duration )
37. val one = HighLow(high = 120, low = 40) // In Microseconds val zero = HighLow(high = 40, low = 120) // In Microseconds val sync = HighLow(high = 2, low = 240) // In Microseconds
38. private fun processData(changeCount: Int): String? { }
39. private fun processData(changeCount: Int): String? { for (i in 1 until changeCount step 2) { } }
40. private fun processData(changeCount: Int): String? { for (i in 1 until changeCount step 2) { code = code shl 1 } }
41. private fun processData(changeCount: Int): String? { for (i in 1 until changeCount step 2) { code = code shl 1 // code = 00 } }
42. Zero
43. private fun processData(changeCount: Int): String? { for (i in 1 until changeCount step 2) { code = code shl 1 // code = 00 if (diff(timings[i],zero.high) < delayTolerance && diff(timings[i + 1],zero.low) < delayTolerance) { // zero, do nothing } } }
44. One
45. private fun processData(changeCount: Int): String? { for (i in 1 until changeCount step 2) { ... } else if (diff(timings[i],one.high) < delayTolerance && diff(timings[i + 1], one.low) < delayTolerance) { // one } } }
46. private fun processData(changeCount: Int): String? { for (i in 1 until changeCount step 2) { ... } else if (diff(timings[i],oneHighDuration) < delayTolerance && diff(timings[i + 1], oneLowDuration) < delayTolerance) { // one code = code or 1 } } }
47. private fun processData(changeCount: Int): String? { for (i in 1 until changeCount step 2) { ... } else if (diff(timings[i],oneHighDuration) < delayTolerance && diff(timings[i + 1], oneLowDuration) < delayTolerance) { // one code = code or 1 // code = 01 } } }
48. private fun processData(changeCount: Int): String? { for (i in 1 until changeCount step 2) { ... else { return null // Invalid code } } }
49. private fun processData(changeCount: Int): String? { for (i in 1 until changeCount step 2) { … else { return null // Invalid code } } return code.asBinaryString() }
50. Now sending
51. private var repeatTimes = 4 fun send(code: String) { }
52. fun send(code: String) { (0..repeatTimes - 1).forEach { } }
53. fun send(code: String) { (0..repeatTimes - 1).forEach { code.forEach { } } }
54. fun send(code: String) { (0..repeatTimes - 1).forEach { code.forEach { if(it == ‘0'){ transmit(one) } else if(it == ‘1') { transmit(zero) } } } }
55. fun send(code: String) { (0..repeatTimes - 1).forEach { code.forEach { if(it == ‘0’){ transmit(one) } else if(it == ‘1') { transmit(zero) } else throw IllegalArgumentException("Only binary code allowed") } } }
56. fun send(code: String) { (0..repeatTimes - 1).forEach { code.forEach { if(it == ‘0’){ transmit(one) } else if(it == ‘1') { transmit(zero) } else throw IllegalArgumentException("Only binary code allowed") } transmit(sync) } }
57. fun send(code: String) { (0..repeatTimes - 1).forEach { code.forEach { if(it == ‘0’){ transmit(one) } else if(it == ‘1') { transmit(zero) } else throw IllegalArgumentException("Only binary code allowed") } transmit(sync) } digitalWrite(false) }
58. private fun transmit(pulse: HighLow) { }
59. private fun transmit(pulse: HighLow) { digitalWrite(true) busyWaitMicros(pulse.high) }
60. private fun transmit(pulse: HighLow) { digitalWrite(true) busyWaitMicros(pulse.high) }
61. Supported I/Os private fun transmit(pulse: HighLow) { digitalWrite(true) busyWaitMicros(pulse.high) digitalWrite(false) busyWaitMicros(pulse.low) }
62. Supported I/Os private fun transmit(pulse: HighLow) { digitalWrite(true) busyWaitMicros(pulse.high) digitalWrite(false) busyWaitMicros(pulse.low) }
63. private fun digitalWrite(value: Boolean) { gpio.value = value } private fun busyWaitMicros(micros: Int) { val waitUntil = System.nanoTime() + micros * 1000 while (waitUntil > System.nanoTime()) { } }
64. This is all great. Does it work?
65. NO!
66. Why?
68. NDK
69. struct HighLow { uint8_t high; uint8_t low; }; const char *GPIO_PORT = "BCM21"; const int repeatTimes = 4; const int LOW = 0; const int HIGH = 1; const HighLow one = {40, 120}; const HighLow zero = {120, 40}; const HighLow sync = {1, 240};
70. void init(){ APeripheralManagerClient *client = APeripheralManagerClient_new(); APeripheralManagerClient_openGpio(client, GPIO_PORT, &gpio); AGpio_setDirection(gpio, AGPIO_DIRECTION_OUT_INITIALLY_LOW); }
71. void send(unsigned long code, unsigned int length) { for (int repeat = 0; repeat < repeatTimes; repeat++) { for (int i = length - 1; i >= 0; i--) { if (code & (1L << i)) transmit(one); else transmit(zero); } transmit(sync); } digitalWrite(LOW); }
72. void transmit(HighLow pulse) { digitalWrite(HIGH); usleep(pulse.high); digitalWrite(LOW); usleep(pulse.low); } void digitalWrite(const int value) { AGpio_setValue(gpio, value) }
73. Now it worked right!?
74. Nope!
77. Now what?
79. Supported I/Os ! General Purpose Input/Output (GPIO): Binary ! Universal Asynchronous Receiver Transmitter (UART) ! Inter-Integrated Circuit(I2C) ! Pulse Width Modulation (PWM): Servo motors, DC motors ! Serial Peripheral Interface (SPI)
80. Raspberry Pi Receiver Transmitter 5v Ground
81. Raspberry Pi Receiver Transmitter 5v Ground Arduino
82. Raspberry Pi Receiver Transmitter 5v Ground Arduino
83. But the Arduino is running at 5v
84. Raspberry Pi Receiver Transmitter 5v Ground Level shifter Arduino
85. val uart = PeripheralManagerService().openUartDevice("UART0") uart.setBaudrate(115200) uart.setDataSize(8) uart.setParity(UartDevice.PARITY_NONE) uart.setStopBits(1) uart.registerUartDeviceCallback(uartDeviceCallback)
86. private val uartDeviceCallback = object : UartDeviceCallback() { override fun onUartDeviceDataAvailable(uart: UartDevice?): Boolean { val buffer = ByteArray(8) while (uart?.read(buffer, buffer.size)!! > 0) { handleData(buffer) } return true } }
87. // Write uart.write(codeAsByteArray)
89. Supported I/Os ! General Purpose Input/Output (GPIO): Binary ! Universal Asynchronous Receiver Transmitter (UART) ! Inter-Integrated Circuit(I2C) ! Pulse Width Modulation (PWM): Servo motors, DC motors ! Serial Peripheral Interface (SPI)
90. Arduino Nano
91. Aren’t you forgetting something?
92. Level shifter
93. RCSwitch lib for Arduino
94. // Arduino const uint8_t I2C_ADDRESS = 0x42;
 void setup() { rcSwitch = RCSwitch(); Wire.begin(I2C_ADDRESS); Wire.onRequest(requestEvent); Wire.onReceive(receiveEvent); }
95. // Arduino
 void loop() { if (rcSwitch.codeAvailable()) { code = rcSwitch.getCode(); bitsize = rcSwitch.getCodeBitSize(); rcSwitch.resetCode(); } }
96. // Arduino const uint8_t COMMAND_REQUEST_BITSIZE = 0x02; const uint8_t COMMAND_REQUEST_CODE = 0x05; void requestEvent() { switch (opcode) { case COMMAND_REQUEST_BITSIZE: Wire.write(bitsize); break; case COMMAND_REQUEST_CODE: Wire.write(code); break; default: Wire.write(0); break; } }
97. // Arduino
 void receiveEvent(int bytes) { opcode = Wire.read(); if (bytes > 1) { if (opcode == CODE_RECEIVED_ACKNOWLEDGE) { Wire.read(); code = ""; bitsize = 0; } } }
98. companion object { private const val I2C_ADDRESS = 0x42 private const val REQUEST_SIZE_IN_BITS = 0x02 private const val REQUEST_CODE = 0x05 private const val CODE_RECEIVED_ACKNOWLEDGE = 0x06 } i2cDevice = PeripheralManagerService().openI2cDevice(portName, I2C_ADDRESS)
99. fun readCode(): String? { val size = i2CDevice.readRegByte(REQUEST_SIZE_IN_BITS).unsignedToInt() // No data if (size == 0) { return null } }
100. fun readCode(): String? { val size = i2CDevice.readRegByte(REQUEST_SIZE_IN_BITS).unsignedToInt() // No data if (size == 0) { return null } val byteArray = ByteArray(size) i2CDeviceService.readRegBuffer(REQUEST_CODE, byteArray, size) val codeInBinary = byteArray.asString() return codeInBinary }
101. // Arduino
 if (opcode == SEND_CODE && bytes > 2) { int codeSize = bytes - 1; String codeReceived = String(); while (Wire.available() != 0) { char c = Wire.read(); Serial.print(c); codeReceived += c; c++; }
102. companion object { private const val SEND_CODE = 0x07 } fun sendCode(code: String) { i2cDevice.writeRegBuffer(SEND_CODE, code.toByteArray(), code.length) }
103. val handler = Handler() val runnable = object : Runnable { override fun run() { readCode() handler.postDelayed(this, 1000) } } handler.postDelayed(runnable, 100)
104. // Arduino
 void loop() { if (rcSwitch.codeAvailable()) { code = rcSwitch.getCode(); bitSize = rcSwitch.getCodeBitSize(); rcSwitch.resetCode(); } }
105. // Arduino
 void loop() { if (rcSwitch.codeAvailable()) { code = rcSwitch.getCode(); rcSwitch.resetCode(); digitalWrite(GPIO_PIN, HIGH); } }
106. // Arduino
 void receiveEvent(int bytes) { opcode = Wire.read(); if (bytes > 1) { if (opcode == CODE_RECEIVED_ACKNOWLEDGE) { Wire.read(); code = ""; bitsize = 0; receivedProtocol = 0; receivedPulseLength = 0; } } }
107. void receiveEvent(int bytes) { opcode = Wire.read(); if (bytes > 1) { if (opcode == CODE_RECEIVED_ACKNOWLEDGE) { Wire.read(); code = ""; bitsize = 0; receivedProtocol = 0; receivedPulseLength = 0; digitalWrite(GPIO_PIN, LOW); } } }
108. gpio.setDirection(Gpio.DIRECTION_IN) gpio.setEdgeTriggerType(Gpio.EDGE_RISING) gpio.registerGpioCallback(listener)
109. private val listener = object : GpioCallback() { override fun onGpioEdge(gpio: Gpio?): Boolean { readCode() return false } override fun onGpioError(gpio: Gpio?, error: Int) { Log.e("TAG", “GPIO Error!") } }
113. Supported I/Os ! General Purpose Input/Output (GPIO): Binary ! Inter-Integrated Circuit(I2C) ! Universal Asynchronous Receiver Transmitter (UART) ! Pulse Width Modulation (PWM): Servo motors, DC motors ! Serial Peripheral Interface (SPI)
114. Supported I/Os https://github.com/jamescoggan/remotecontrolarduino ! Library ! Tests ! Example app ! Arduino files ! Diagrams (pending) Separate repo: ! GPIO code (the one that didn’t work)
115. Thank you! https://jamescoggan.com @mad_team https://github.com/jamescoggan/remotecontrolarduino