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Wireless Embedded Systems (0120442x) Sensor Node Programming II (UART and Radio)

Wireless Embedded Systems (0120442x) Sensor Node Programming II (UART and Radio). Chaiporn Jaikaeo chaiporn.j@ku.ac.th Department of Computer Engineering Kasetsart University. Outline. UART communication Single-hop radio communication. Connecting Mote to PC.

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Wireless Embedded Systems (0120442x) Sensor Node Programming II (UART and Radio)

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  1. Wireless Embedded Systems(0120442x) Sensor Node Programming II(UART and Radio) Chaiporn Jaikaeo chaiporn.j@ku.ac.th Department of Computer EngineeringKasetsart University

  2. Outline • UART communication • Single-hop radio communication

  3. Connecting Mote to PC • USB connector on IWING-MRF and IWING-JN • USB dongles 3.3VRXTXGND 3.3V5VRXTXGND USB Dongle based on SiliconLab’s CP2102 ThaiEasyElec’s USB Dongle (FDTI)

  4. UART API (motelib/uart.h) • Enable UART (both TX and RX) • Send a single byte over UART • Send multiple bytes over UART uartEnable(true,true); uartWriteByte(50); uint8_t buf[10]; : uartWrite(buf, 10);

  5. UART API (cont'd) • Check whether there is any data received from UART • Read a single byte from UART input buffer • Send formatted string over UART using Standard I/O library if (uartInputLen() > 0) ... uint8_t byte = uartReadByte(); #include <stdio.h> : : printf("Hello, world\n"); printf("i = %d\n", i);

  6. Processing UART Data on PC • Locate UART device file • Run dmesg to find out • Usually /dev/ttyUSB0 or /dev/ttyACM0 • For textual data • Run terminal program such as screen, gtk-term, putty on UART device • For binary data • Any UART library can be used • E.g., Python's serial package $ dmesg : [70063.712091] usb 4-1: new low speed USB device using uhci_hcd and .. [70063.871042] usb 4-1: config 1 interface 1 altsetting .. [70063.871056] usb 4-1: config 1 interface 1 altsetting .. [70063.895220] cdc_acm 4-1:1.0: ttyACM0: USB ACM device

  7. USB-UART Implementation • MoteLib provides UART-via-USB implementation for IWING-MRF platform (>= rev. 388) • Emulated using V-USB library by Objective Development • Based on AVR-CDC project (http://www.recursion.jp/avrcdc/) • Requires no USB dongle • Build your app with UART_VIA_USB=1 $ make UART_VIA_USB=1 ...

  8. Example: sense-to-uart.c • Sense light intensity every second; send values to display via UART void senseDone(uint16_t value) { printf("Light = %d\n", value); actorSetState(ACTOR_0, 0); } void sense(Timer *t) { actorSetState(ACTOR_0, 1); sensorRequestAnalog(SENSOR_1, senseDone); } #include <stdio.h> #include <motelib/system.h> #include <motelib/timer.h> #include <motelib/uart.h> #include <motelib/sensor.h> #include <motelib/actor.h> Timer t; void senseDone(uint16_t value); void sense(Timer *t); void boot() { uartEnable(true,true); timerCreate(&t); timerStart(&t, TIMER_PERIODIC, 1000, sense); }

  9. Testing sense-to-uart • Build with UART_VIA_USB option • Capture UART output using screen(or gtk-term or putty) $ make UART_VIA_USB=1 flash $ screen /dev/ttyACM0

  10. Radio Communication • IWING-MRF: Microchip's MRF24J40 controller • IWING-JN: Built-in • IEEE 802.15.4 @ 2.4 GHz, 250 kbps • 16 non-overlapping channels • 16-bit node ID • 16-bit PAN (Personal Area Network) ID

  11. Configuring Radio (IWING-MRF) • Use config-mote.py script located in $MOTELIB_DIR/platforms/iwing-mrf/tools • Have mote enter bootloader, then run: • E.g., set address to 234 and PAN ID to 555 • Set channel to 0x1A $ cd $MOTELIB_DIR/platforms/iwing-mrf/tools $ ./config-mote.py $ ./config-mote.py --address 234 --panid 555 $ ./config-mote.py --channel 0x1A

  12. Configure Radio (IWING-JN) • Set the following variables via make • DEFAULT_ADDR • DEFAULT_PANID • DEFAULT_CHANNEL • Example: $ make PLATFORM=iwing-jn DEFAULT_ADDR=50

  13. Radio Message Format • Type and application data are provided by the application via Radio API 802.15.4 Header Type(1 byte) Seq No.(1 byte) App Data(max ~100 bytes) Checksum

  14. Radio API (motelib/radio.h) • Broadcast a message (type=7) containing "HELLO" to all neighbors • Call txDone() when message has been sent • Use NULL when callback is not needed radioRequestTx(BROADCAST_ADDR, 7, "HELLO", 5, txDone); : void txDone(RadioStatus status) { : } radioRequestTx(BROADCAST_ADDR, 7, "HELLO", 5, NULL);

  15. Radio API (cont'd) • Set a handler to process received messages radioSetRxHandler(receive); : void receive(Address src, MessageType type, void *msg, uint8_t len) { : }

  16. Example: sense-to-base.c • Every second, each sensor node measures light intensity and reports to the base station • Assume base station has address = 0 • Base station reports light measurements over UART Base station Sensor node Sensor nodes measuring light intensity

  17. sense-to-base.c #include <motelib/system.h> #include <motelib/timer.h> #include <motelib/radio.h> #include <motelib/sensor.h> #include <motelib/actor.h> Timer t; void sense(Timer *t); void senseDone(uint16_t value); void boot() { timerCreate(&t); timerStart( &t, TIMER_PERIODIC, 1000, sense); } void sense(Timer *t) { actorSetState(ACTOR_0, 1); sensorRequestAnalog( SENSOR_1, senseDone); } void senseDone(uint16_t value) { radioRequestTx(0, 1, &value, sizeof(value), NULL); actorSetState(ACTOR_0, 0); }

  18. base.c #include <stdio.h> #include <motelib/system.h> #include <motelib/radio.h> #include <motelib/uart.h> void receive(Address src, MessageType type,void *msg, uint8_t len) { if (type == 1) { printf("Node %d: Light = %d\n", src, *((uint16_t*)msg)); } } void boot() { uartEnable(true,true); radioSetRxHandler(receive); }

  19. Exercise: Voting Machine • Create an application for wireless voting machine • Allow user to cast a vote using the USER button • Voting choices are: Red (1), Yellow (2), Green (3), or No Vote (0) • When the USER button is pressed, • Set LED status accordingly • Report current vote to the base station (#1) with message type 50

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