2008 KOP IR Sensor Workshop

1. 2008 KOP IR Sensor Workshop January 12, 2008 Hauppauge High School SPBLI - FIRST Mark McLeod Advisor Hauppauge Team 358 Northrop Grumman Corp. Mark.McLeod@ngc.com

2. IR Board

3. Cautions • Beware Hooking Power Up Backwards! • Safer to test with 9v battery first • Beware Static Electricity! • Place on non-conductive surface (the bag it comes in is conductive) • Ground yourself while touching the board • Compatible IR Remote May need to test with several models of IR remotes to find a compatible frequency/protocol (universal remotes should work) • A few H/W failures have been reported • Failure to work at all • Partial operation • Broken while using

4. Training the IR Sensor • Needed: • IR Remote, IR sensor board/cable, 9v battery, 2 alligator leads to connect the battery • Learn: • Hold button down, add power, hold 2 secs, release • LEDs • Error, cmd0, cmd1, cmd2, cmd3 http://www.usfirst.org/uploadedFiles/Community/FRC/FRC_Documents_and_Updates/2008_Assets/FIRSTIR%20-%20Instructions%20_121007.pdf

5. Wiring to Robot Controller • 12v power & ground • Go to breaker panel on robot--Recommend 9v battery to practice with (less chance of accidental damage) • +7-15v --Pins 1/2 • Ground --Pins ¾ • Possible to use fully charged 7.2v backup battery • (4) RC Signal pins • Go to signal pins on Robot Controller • Cmd0 --Pin 8 • Cmd1 --Pin 6 • Cmd2 --Pin 5 • Cmd3 --Pin 7

6. Code • Slow enough (.1 sec) to check from the slow loop (.026 sec)—active for 3 to 4 slow loops • Signals: • All 0’s if none are selected • If using a separate 9v battery then they are all 1’s • All 1’s if nothing is connected or connection is loose • “1” if selected by IR remote, “0” if not selected • Save selection, don’t use signal pin directly—chance of half & half state and it will change while using it

7. Powering the IR Sensor • Normally powered from a 12v breaker • Can be powered from the fully charged 7.2v backup battery • If the voltage drops too low the IR sensor will stop operating • Special Note when testing with a 9v battery: • If 9v battery is used on a Robot Controller the input pins at rest will all register “1” (ground is not common) • If using the same 7.2v or 12v power as the Robot Controller the input pins at rest will register “0” (common ground) • So the code is slightly different for independent 9v battery testing

8. Coding Notes • The IR sensor signal will start and last for 3 or 4 of our slow loops • At the end of the signal there is a window where some pins can start to change & be in an intermediate state • Capture the value of the pins all at once or when they first start to be received and you’ll avoid any half & half states

9. Sample Code -- version 1Checking individual pins char IR_cmd0=0, IR_cmd1=0, IR_cmd2=0, IR_cmd3=0; //declare as extern to use elsewhere // Can use a single “IR_cmd” variable to indicate the command received (1,2,3,4) void Process_Data_From_Local_IO(void) { static char latch=0; if (latch == 1) { //**** Use this check when an independent 9v battery to power the IR Sensor // if (rc_dig_in15 == 1 && rc_dig_in16 == 1 && rc_dig_in17 == 1 && rc_dig_in18 == 1) // **** Use this check when the Robot Controller 7.2v or 12v powers the IR Sensor if (rc_dig_in15 == 0 && rc_dig_in16 == 0 && rc_dig_in17 == 0 && rc_dig_in18 == 0) // Normal common ground { latch = 0; // Avoid being caught by a half & half state of the IR sensor by taking the first change } } else if (rc_dig_in15 == 0 || rc_dig_in16 == 0 || rc_dig_in17 == 0 || rc_dig_in18 == 0) { // Checking the pins individually like this can leave a window for the IR sensor to change in the middle // We avoid that problem by taking only the first change, but a better way would be to capture the pins all at once. //When the IR Sensor sends us a command it will stay steady for at least four or more times before the next change IR_cmd0 = rc_dig_in15; IR_cmd1 = rc_dig_in17; IR_cmd2 = rc_dig_in18; IR_cmd3 = rc_dig_in16; latch = 1; } }

10. Sample Code Use – version 1 extern char IR_cmd0, IR_cmd1, IR_cmd2, IR_cmd3; void Default_Routine(void) { if (IR_cmd0 == 1) { pwm01 = 127; pwm02 = 127; } else if (IR_cmd1 == 1) { pwm01 = 254; pwm02 = 0; } else if (IR_cmd2 == 1) { pwm01 = 0; pwm02 = 254; } else if (IR_cmd3 == 1) { pwm01 = 254; pwm02 = 254; } }

11. Sample Code – Better VersionGrabbing all the pins at once switch(IR_cmd) case 1: pwm01 = 127; pwm02 = 127; break; case 2: pwm01 = 254; pwm02 = 0; break; case 3: pwm01 = 0; pwm02 = 254; break; case 4: pwm01 = 254; pwm02 = 254; } } Void Default_Routine(void) { static char latch=0; unsigned char sensorReading; //**** Check the IR Sensor for a new command sensorReading = PORTJ>>4; // Combined digital inputs 15-18 if (latch == 1) { if (sensorReading == 0) { latch = 0; // Take only the 1st reading to avoid // being caught by a half & half state of the IR sensor } } else if (sensorReading != 0) { latch = 1; if (sensorReading == 8) IR_cmd = 1; else if (sensorReading == 4) IR_cmd = 4; else if (sensorReading == 2) IR_cmd = 2; else if (sensorReading == 1) IR_cmd = 3; }

12. Potential Use Four Commands ONLY (but can be a different set each match) • Basic Drive Control: • forward, reverse, left, right • forward, left, right, raise arm to hit ball • Left, right, arm up, arm down • Autonomous Assist: • Trackball position-left / center / right • Trigger to hit ball • Stop current action and go to next pre-programmed act • Driver Assist: • Signals to help herd ball on far side of field, make turns, negotiate traffic jams

13. Issues • Range of IR Remote (power) • Duplicate IR remotes/protocols/buttons • Repeat or once only IR signal • Repeat will case more interference • Once only may be hard to drive by • IR Interference with partners and opponents • Coordinate w/ Alliance partners • May get through less frequently or not at all • Sensor blocked from Robocoach at times • Turn is 180 degrees • Center wall may reflect IR

14. Suggestions • Make sensor directional, E.g., tube • Closer / more power can override interference • Plan for the IR commands to fail and still have your robot accomplish something during Hybrid, e.g., • Basic auto command to drive straight to get the first 4 points • Further action commanded by Robocoach at far end controlling the turn and backstretch • Shield sensor from overhead ambient light • Watch the FIRST Q&A for rulings that change things

15. Alternatives • Can modify the IR sensor to another frequency by replacing the sensor • Can use a different technology within the rules, e.g. no lasers, to send your four commands to the robot during Hybrid Mode • Visible light • Sound • Replacement www.vishay.com • Equivalent TinyIR2 • http://www.tauntek.com/tinyir2-learning-ir-remote-control-receiver.htm

16. Lap Counter • Mounts on your flag holder-- The top of the holder must be 51” high • 180 degree horizontal arc around the top of the flag holder must be kept clear within a 2-inch radius and be uncovered and visible from above. • The LAP INDICATOR is powered via a standard three-wire PWM cable. An easily accessible, powered, male PWM connector must be located at the top of the flag holder • Distributed for each match • Details at http://www.rclapcounter.com/