Gas station without pumps

2011 September 27

4pcb.com sticklers for the $50 multiple-image surcharge

4pcb.com put a hold on my second order from them, asking for an extra $50 (bringing the cost up to $100.30) for the new board, because there were multiple images.

I asked them on the phone what the rule was now for defining multiple images.  Although they did not give an exact algorithm, basically they are looking for separate pieces unconnected by copper traces.  I suspect that they either do a quick look at the board manually or have some very crude program to detect probable repeats.

They are not looking just for exact repeats (which is the rule that Gabriel Elkaim told me they used), but anything that looks like multiple boards. Now I have to decide whether to pay the $50 surcharge, find another vendor, or redesign the board.

For the tiny breakout boards I may be better off with a BatchPCB.com order, at $2.50/sq in + $10 setup. I had 3 (slightly different) copies of the hexmotor 2.3 board, plus 2 each of 3 different breakout board designs for the pressure sensor.

The areas and prices for the boards (not including shipping) are

board dimensions area BatchPCB.com price
pressure 1.3 0.7″ × 1.45″ 1.015 sq in $15.08 for 2
pressure 1.4 1.5″ × 1.0″ 1.5 sq in $17.50 for 2
pressure 1.5 0.475″ × 0.8″ 0.38 sq in $15.00 for 2
hexmotor 2.3 3.95″ × 3.15″ 12.44 sq in $41.11 for 1, $103.32 for 3
combined 7.537″ × 6.737″ 50.78 sq in $136.94 for 1

So if I keep the original order, I’m better off with 4pcb.com pricing, but if I get only 1 motor controller board, I could reduce the price to about $75+shipping (with a new combined board, to avoid the repeated $10 setup).  If I just want the breakout boards, I could do all of them without the hexmotor board as 2 copies of  a combined 1″ × 3.825″ board  for $29.13+shipping.

UPDATE: I decided I want the new features of the hexmotor 2.3 board enough to spend the extra $60 rather than just using the old hexmotor 1.3 board.  When I want tiny boards, though, I’ll try BatchPCB.com, which will be cheaper for boards smaller than about 13 square inches (depending on shipping and how many are ordered).

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2011 September 23

New board designed

I’ve just sent a new set of boards for fab.  The HexMotor rev2.3 boards have several new features: LEDs for +5v and +6.25v, a reset button, 16-bit shift register instead of 8-bit, servo outputs connected to pins 13, 7, 2, 9, 10 (rather than to the pins used for PWM).  The new board should be able to do either 6 PWM motors or 4 PWM motors, 5 servos, and 2 non-modulated reversible motors.

I’m also making some breakout boards for the MPXHZ6250A pressure sensors from Freescale Semiconductor, which will require doing some SMD soldering.  At least the design uses gull-wing pins, which can (supposedly) be hand soldered.  One of the breakout boards also has a place for mounting an ADXL335 accelerometer, which may be more difficult to solder.  I don’t think I want to spend the money for a hot-air rework station, and I’m a bit dubious about my ability to solder using a toaster oven.

The pressure sensors are tiny!  My original suggestion to the robotics club was to drill a hole in the dry box and superglue the pressure sensor to the inside of the box (after the pressure sensor had been attached to the breakout board, of course).  Now I’m not so sure that there will be enough glue area to hold firmly enough.  Perhaps a dab of some sealant on the outside of the box might help, if we can keep from plugging the hole in the sensor.

The breakout board that I think that the robotics club will end up using puts a pressure sensor on one side and headers for a piggyback ADXL335 breakout board on the back.  that way there only need to be one set of wires for connecting the analog inputs and power to the sensors.

One limitation of the Arduino for use with this combination of sensors is that the accelerometer is a 3v part and the pressure sensor is a 5v part. We’ll have to set up the analog-to-digital converter on the Arduino to have a 5v range, which reduces the precision of the acceleration readings.

I’ve also bought some other sensors (not for the underwater vehicle, but for physics class and dry robotics): a couple of ultrasonic rangefinders.  More on those in a separate post, after I’ve had a chance to play with them.

2011 August 9

Board fully populated and tested

Top view of the HexMotor rev 1.3 board fully populated.

I got the board fully populated yesterday, plus I made a heat sink out of a piece of ¼” × ¾” aluminum bar stock.  The heat sink makes an enormous difference.  Before using it, running a small motor at low power for 20–30 seconds was enough to make the H-bridge uncomfortably hot.  Now running the same 12v motor stalled at full current (3A) for a full minute raises the temperature only to 100ºF.

The motor got warmer than that, and I think I burned it out, since it no longer runs and has a 400kΩ resistance.  I’m not really surprised—it was a cheap door-lock actuator, and only intended to be used with fraction of a second pulses.  Further testing will require a more robust motor.

As you can see from the photo, the screw terminal for motor 4 (second from the bottom) is a bit crooked—I’ll have to unsolder it and straighten it.  For the HexMotor 2 board, I’ll use slightly smaller holes so alignment is easier.

The thermal grease I used (Cooler Master IceFusion High Performance Thermal Compound 40G RG-ICF-CWR2-GP) was more liquid than I expected, especially since it comes with a little spatula for applying it.  I had to put on a fairly thick layer, because the aluminum extrusion was not very smooth, and when I tightened the bolts the stuff oozed out making a sticky mess. Next time, I’ll sand the aluminum smooth first and use much less thermal grease.

Closeup, showing the excess thermal grease puddling under the H-bridges, where it is very difficult to wipe off.

This closeup photo, in addition to showing the pooled excess thermal grease, shows the header pins with shorting jumpers to configure the H-bridges for either lock antiphase or sign-magnitude control.  (Because of the last-minute change from TLE-5205 to TLE-5206 chips, the silk-screen labeling of the header pins is wrong—this board is actually configured for sign-magnitude throughout not lock antiphase.

The photos also show that I did not leave room for the heat sink between the electrolytic capacitors.  The HexMotor 2.0 board will fix this problem also.

The HexMotor software now can handle 3 different boards: the HexMotor rev 1.3 board shown here, the Adafruit Motor Shield, and the HexMotor rev 2 board, which I am just about done fussing with the design for.  I’ve only tested with an Arduino Duemilanove board, but the software should work with an Arduino Mega as well.

2011 August 6

HexMotor.h expanded to Adafruit Motor shield

Filed under: Hexmotor H-bridge board,Software — gasstationwithoutpumps @ 16:33
Tags: , , ,

I expanded the HexMotor.cc and HexMotor.h library today, so that I can use the same library with both my HexMotor board and the Adafruit Industries motor shield.  The only differences from a user’s standpoint are

  • Declare an AdafruitMotorBoard instead of HexMotorBoard.
  • Use motors 1,2,3,4 instead of 0,1,2,3,4,5.
  • motor.release() works on the AdafruitMotorBoard, but is not usable on the HexMotorBoard, which only brakes when off.

I also figured out a way to get some debugging capability into the library, so that people could check that their configuration is consistent (though there is no way to check whether the jumpers and wiring are actually what the user says they are supposed to be).  I can’t use “assert” statements the way I’m used to, so I did explicit if-statements and provided output through Serial.print() calls.  This only works for tests that come after the Serial.begin() call, so I put the tests in the HexMotorBoard::setup() method, assuming that it would be called after Serial.begin() in setup().

The tests can be turned off by commenting out the #define HEX_MOTOR_DEBUG 1 line in the HexMotor.h file, reducing the size of the downloaded program by 860 bytes.  Actually, almost everyone will have to turn the debugging off, since every run() command sends debugging output to the serial line, so the default is to have the debugging off.

The software library is pretty much done for controlling brushed motors, except for changing PWM frequency.  Currently motors 0 and 1 (1 and 2 on the Adafruit board) run at 490Hz, while motors 2 and 3 (3 and 4 of the Adafruit board) run at 976.5Hz and motors 4 and 5 at 490Hz.  I don’t want to mess with the PWM for motors 2 and 3, since that timer is also used for the delay() and millis() calls, so I probably want to change the PWM frequency for the other PWM pins.

Update 8 October 2011: Since I’ve just found out how to put source code into WordPress blogs, let me put the latest versions of HexMotor.h and HexMotor.cpp here:

// HexMotor.h
// copyright Kevin Karplus 8 August 2011
// Creative Commons license Attribution-NonCommercial
//	http://creativecommons.org/licenses/by-nc/3.0/

#ifndef _HexMotor_h_
#define _HexMotor_h_

#include <inttypes.h>
#include <avr/io.h>

// Define HEX_MOTOR_DEBUG if you want to get error messages from setup() for erroneous setup.
// #define HEX_MOTOR_DEBUG 1

// Declaring a HexMotorBoard gives the jumperable configuration for the board.
// The relevant jumpers are which pins drive the motor speed inputs
// and whether the H-bridges are configured for lock antiphase or sign-magnitude.
//
// IN2 of the H-bridge is always connected to SIGN XOR MAG
//
// IN1 of the H-bridge can be connected to either SIGN  or MAG.
//		If IN1 is connected to SIGN, then the TLE-5206 H-bridge will
//			be running in a sign magnitude mode, with the Speed pin low meaning BRAKE
//				and Speed pin high meaning RUN (with the sign bit indicating which way to turn).
//		If IN1 is connected to MAG, then the TLE-5206 H-bridge will
//		    be in lock antiphase, running if the SIGN bit is high and BRAKING if the SIGN bit is low.
//			The MAG bit determines which way the motor runs.
//      If the MAG bit is not a PWM output, then IN1 should be connected to MAG.
// Note: on the rev 1.3 boards, the silkscreen for the jumpers is misleading.  
//      The center of the 5 holes for header pins is MAG and the outer one is SIGN.

// The PWM frequency for all channels defaults to 1kHz (actually 16Mz/ 2^14 = 976.56Hz)
// Changes could be made in the HexMotorBoard::setup() routine if other PWM frequencies are needed.


class HexMotorBoard
{ protected:
	uint8_t SpeedPins[6];
	    // which pins are connected to the "speed" (MAG) inputs of each H-bridge?
	    // Numbers 0-54 are for Arduino pins
	    // Numbers 0xA0..0xA7 are for the low byte of the serial output latch
	    // Numbers 0xA8..0xAF are for the high byte of the serial output latch
		//		(on rev2 or later)
		// Number 0xFF means that the MAG bit is tied to +5V
	    // 
	    // Note: all SpeedPins should be connected to something.
		
	
	    // Note: on Arduinos other than Mega, using the Servo library means that pins 9 and 10
	    // are not PWM pins.  If used, they should be set up as ON/OFF pins. 
	
	
	enum{NOT_THERE, SIGN_MAG, ANTIPHASE, FORWARD_BACKWARD_BRAKE, ONE_BIT, ADAFRUIT} MotorMode[6];	// MotorMode[i] is
				// NOT_THERE if motor_i is not usable on this board
				// SIGN_MAG if IN1 of motor i is connected to SIGN, and MAG is assumed to be PWM
				// ANTIPHASE if IN1 of motor i connected to MAG and MAG is a PWM bit
			    // FORWARD_BACKWARD_BRAKE if IN1 of motor i connected to MAG, but MAG is ON/OFF, not PWM.
				// ONE_BIT if IN1 is connected to MAG, which is tied to +5v, so the
			    //		the motor is always either running forward or backward, controlled by the SIGN bit
				// ADAFRUIT if this is not a HexMotor board, but an Adafruit Motor shield
				//
	
	uint8_t LatchPin, ClockPin, DataPin;
		// which Arduino pins are used for talking to the Hexmotor shift register?
	
	uint16_t ShiftRegister;  // the current or future contents of the HexMotor shift register
	
	uint8_t Version;	// which model of board is used
	
	// set (or clear) a bit in the ShiftRegister corresponding to the specified motor
	inline void set_signbit(uint8_t motor, bool value=1)
	{   digitalWrite(0xA0+motor, value);
	}  
	
	void serial_out(void);	// transfer the shift register to the HexMotor board.
  public:
	HexMotorBoard(
				  const char *antis, 
				  const uint8_t *pins=0,	// defaults to {11, 3, 6, 5, 9,10}
				  uint8_t version=1,
				  uint8_t clock=4, 
				  uint8_t data=8, 
				  uint8_t latch=12);
	    // An array of pins is given to indicate where the MAG output for each motor goes.
					
	    // The 6 antis characters are 
		// '-' for NOT_THERE
		// 'S' or 's' for SIGN_MAG (IN1==SIGN)
	    // 'A' or 'a' for ANTIPHASE (IN1==MAG) 
	    // 'F' or 'f' for FORWARD_BACKWARD_BRAKE (IN1==MAG, but MAG is not PWM bit)
		// 'O' or 'o' for ONE_BIT
		// 'M' or 'm' for ADAFRUIT motor shield
		
		// The version is the integer part of the board rev number (rev1.3 is 1, rev 2.3 is 2).
	    // This indicates, for example, whether the board has 8 or 16 bits of shift register.
		// Use rev 0 to indicate an Adafruit motorshield.
	    // latch, data, and clock are Arduino pins that are used for the serial output to the shift register. 
	
	void setup(void);
	    // makes sure that PWM frequencies are appropriately set and turns all motors off.
	    // Should be called during the global setup() procedure.
	    // QUERY: should PWM frequency be settable here (or even as separate call?)
	
	void digitalWrite(uint8_t pin, bool value);	// write a single bit to a pin (using SpeedPins naming convention)
	friend class HexMotor;
};



// Declaring an AdafruitMotorBoard sets up the HexMotorBoard interface for an AdaFruit Industries Motor Shield, 
// rather than for a HexMotor board.
// The declaration has no parameters, as the AdaFruit motor shield is not configurable.
// For compatibility with the M1 through M4 labeling on the motor shield, motors 1 through 4 are used,
// rather than 0 through 3.

class AdafruitMotorBoard : public HexMotorBoard
{  protected:
	typedef enum{FORWARD, BACKWARD, BRAKE} MotorDir;
	void change_motor_bits(uint8_t motor,  MotorDir control);
  public: 
	AdafruitMotorBoard(void);
   	friend class HexMotor;

};



class HexMotor 
{  protected: 
	uint8_t Motor;
	HexMotorBoard* Board;

  public:
	HexMotor(HexMotorBoard &board, uint8_t motor_num);
	
	void run(int speed);
	// speed is between -256 (full reverse) and 255 (full forward)
	// 0 is off (braking on HexMotor, released on Adafruit)
	
	void brake(void);

	void release(void);		// Available on Adafruit Motor shield,
							// but not on HexMotor boards rev1 or rev 2
							// since the TLE-5206 chips do not have a Hi-Z output
};


#endif
// HexMotor  library
// Kevin Karplus
//copyright 8 August 2011
//	http://creativecommons.org/licenses/by-nc/3.0/

#include <avr/io.h>
#include <pins_arduino.h>
#include <WProgram.h>
#include "HexMotor.h"

// The PWM frequency for all channels defaults to 1kHz.
// Changes could be made in the HexMotorBoard::setup() routine if other PWM frequencies are needed.

// The frequencies below are approximate.
// The actual frequency in fast PWM mode is f_clk/(256*prescale)
// For the 16.000MHz crystal of the Arduino, the frequencies are
// 62.5KHz, 7.125KHz, 1.9531 kHz, 976.56Hz, 488.28Hz, 244.14 Hz, and 61.035Hz

// Don't mess with timer 0, since it is used for "delay()" and "millis()"
#define OCR0_64KHz (1)  // no prescale
#define OCR0_8KHz (2)   // divide by 8
#define OCR0_1KHz (3)  // divide by 16

// Timer 1 (and Timers 3, 4, 5 on Arduino Mega) have limited
//	prescale choices, because they allow external clock as well.
#define OCR1_62KHz	(1)	// no prescale
#define OCR1_7KHz	(2)	// divide by 8
#define OCR1_1KHz	(3)	// divide by 64
#define OCR1_240Hz	(4)	// divide by 256
#define OCR1_61Hz	(5)	// divide by 1024

#define OCR2_62KHz	(1)	// no prescale
#define OCR2_7KHz	(2)	// divide by 8
#define OCR2_2KHz	(3)	// divide by 32
#define OCR2_1KHz	(4)	// divide by 64
#define OCR2_490Hz	(5)	// divide by 128
#define OCR2_240Hz	(6)	// divide by 256
#define OCR2_61Hz	(7)	// divide by 1024

// The Adafruit Motor Shield has an extra output bit for its serial interface:
#define AdafruitEnablePin (7)

/////////////////
// HexMotorBoard
/////////////////
const uint8_t defaultPins[6]={11, 3, 6, 5, 9,10};

HexMotorBoard::HexMotorBoard(
							 const char *antis,
							 const uint8_t *pins,
							 uint8_t version,
							 uint8_t clock,
							 uint8_t data,
							 uint8_t latch)
{
	if (pins==0) {pins= defaultPins;}
	// Save all the jumper information.
	for(int8_t i=5; i>=0; i--)
	{   SpeedPins[i] = pins[i];
		switch (antis[i]) {
			case 'A': case 'a':
				MotorMode[i] = ANTIPHASE;
				// should check that pins[i] is legal PWM pin
				break;
			case 'S': case 's':
				MotorMode[i] = SIGN_MAG;
				// should check that pins[i] is legal PWM pin
				break;
			case 'F': case 'f':
				MotorMode[i] = FORWARD_BACKWARD_BRAKE;
				// should check that pins[i] is consistent with board version
				break;
			case 'O': case 'o':
				MotorMode[i] = ONE_BIT;
				// should check that pins[i] is 0xFF (indicating MAG tied to +5v)
				break;
			case 'M': case 'm':
				MotorMode[i] = ADAFRUIT;
				// should check that 1<=i<=4 and pins[i]=AdafruitDefaultPins[i] and version==0
				break;

			default:
				MotorMode[i] = NOT_THERE;
				break;
		}
	}
	Version=version;
	ClockPin=clock;
	DataPin=data;
	LatchPin=latch;
}

void HexMotorBoard::setup(void)
{
	// setup the serial output pins and clear the shift register
	pinMode(LatchPin, OUTPUT);
	pinMode(DataPin, OUTPUT);
	pinMode(ClockPin, OUTPUT);
    if (Version==0)
    {   pinMode(AdafruitEnablePin, OUTPUT);
    }

	ShiftRegister=0;
	serial_out();

	for (int8_t m=5;m>=0;m--)
	{
		switch (MotorMode[m])
		{   case NOT_THERE: case ONE_BIT:
#ifdef HEX_MOTOR_DEBUG
			    if (SpeedPins[m]!=0xFF)
			    {   Serial.print(m,DEC);
				    Serial.println(" motor shouldn't have speed pin");
			    }
#endif
		        continue;

			case FORWARD_BACKWARD_BRAKE:
				if (SpeedPins[m] >= 0xA0)
				{
#ifdef HEX_MOTOR_DEBUG
					if (Version<2 && SpeedPins[m]>0xA7)
					{   Serial.print(m,DEC);
						Serial.println(" motor has SpeedPin>0xA7");
					}
#endif
					continue;	// no need to set pinMode for HexMotorPins
				}
				pinMode(SpeedPins[m], OUTPUT);
				continue;	// no PWM to check

			case ADAFRUIT:
#ifdef HEX_MOTOR_DEBUG
				if (Version!=0)
				{   Serial.print(m,DEC);
					Serial.print(" mode M, but board version");
					Serial.println(Version,DEC);
				}
#endif
				break;

			default:
				break;

		}

		if (SpeedPins[m] >= 0xA0)
		{   // A HexMotor shift register output or tied to +5v, can't do PWM.
#ifdef HEX_MOTOR_DEBUG
			Serial.print(m,DEC);
			Serial.print(" motor has one-bit speed in mode ");
			Serial.println(MotorMode[m]);
#endif
			continue;
		}

		//real Arduino pin (not HexMotor shift register)
		pinMode(SpeedPins[m], OUTPUT);

		// Set up PWM frequency
		switch (digitalPinToTimer(SpeedPins[m])) {
			case NOT_ON_TIMER:
#ifdef HEX_MOTOR_DEBUG
				    Serial.print(m,DEC);
					Serial.print(" pin ");
					Serial.print(SpeedPins[m]);
					Serial.println(" not a PWM pin");
#endif
				break;

			// timer 0 is used for delay() and millis(),
			// so don't mess with its frequency
			case TIMER0A:
				TCCR0A =  (TCCR0A & 0x30) | _BV(COM0A1) | _BV(WGM00) | _BV(WGM01); // fast PWM, turn on OC0A
				OCR0A = 0;
				break;
			case TIMER0B:
				TCCR0A =  (TCCR0A & 0xC0) | _BV(COM0B1) | _BV(WGM00) | _BV(WGM01); // fast PWM, turn on OC0B
				OCR0B = 0;
				break;

			// Timer 2 is used for pins 11 and 3 of Arduino (not Arduino Mega)
			// default pins for motors 0 and 1, (M1 and M2 on Adafruit Motor shield)
			case TIMER2A:
				TCCR2A = (TCCR2A & 0x30) | _BV(COM2A1) | _BV(WGM20) | _BV(WGM21); // fast PWM, turn on oc2a
				TCCR2B = OCR2_1KHz & 0x7;
				OCR2A = 0;
				break;
			case TIMER2B:
				TCCR2A =  (TCCR2A & 0xC0) | _BV(COM2B1) | _BV(WGM20) | _BV(WGM21); // fast PWM, turn on oc2b
				TCCR2B = OCR2_1KHz & 0x7;
				OCR2B = 0;
				break;

			// Timer 1
			case TIMER1A:
				TCCR1A = (TCCR1A & 0x3C) | _BV(COM1A1) | _BV(WGM10); // fast PWM 8-bit, turn on oc1a
				TCCR1B = (OCR1_1KHz & 0x7) | _BV(WGM12);
				TCCR1C = 0;
				OCR1A = 0;
				break;
			case TIMER1B:
				TCCR1A  = (TCCR1A & 0xCC) | _BV(COM1B1) | _BV(WGM10); // fast PWM 8-bit, turn on oc1b
				TCCR1B = (OCR1_1KHz & 0x7) | _BV(WGM12);
				TCCR1C = 0;
				OCR1B = 0;
				break;
#if defined(__AVR_ATmega1280__) || defined(__AVR_ATmega2560__)
			// Timer 3
			case TIMER3A:
				TCCR3A = (TCCR3A & 0x3C) | _BV(COM3A1) | _BV(WGM10); // fast PWM 8-bit, turn on oc3a
				TCCR3B = (OCR1_1KHz & 0x7) | _BV(WGM12);
				TCCR3C = 0;
				OCR3A = 0;
				break;
			case TIMER3B:
				TCCR3A  = (TCCR3A & 0xCC) | _BV(COM3B1) | _BV(WGM10); // fast PWM 8-bit, turn on oc3b
				TCCR3B = (OCR1_1KHz & 0x7) | _BV(WGM12);
				TCCR3C = 0;
				OCR3B = 0;
				break;
			case TIMER3C:
				TCCR3A  = (TCCR3A & 0xF0) | _BV(COM3C1) | _BV(WGM10); // fast PWM 8-bit, turn on oc3c
				TCCR3B = (OCR1_1KHz & 0x7) | _BV(WGM12);
				TCCR3C = 0;
				OCR3C = 0;
				break;

			// Timer 4
			case TIMER4A:
				TCCR4A = (TCCR4A & 0x3C) | _BV(COM4A1) | _BV(WGM10); // fast PWM 8-bit, turn on oc4a
				TCCR4B = (OCR1_1KHz & 0x7) | _BV(WGM12);
				TCCR4C = 0;
				OCR4A = 0;
				break;
			case TIMER4B:
				TCCR4A  = (TCCR4A & 0xCC) | _BV(COM4B1) | _BV(WGM10); // fast PWM 8-bit, turn on oc4b
				TCCR4B = (OCR1_1KHz & 0x7) | _BV(WGM12);
				TCCR4C = 0;
				OCR4B = 0;
				break;
			case TIMER4C:
				TCCR4A  = (TCCR4A & 0xF0) | _BV(COM4C1) | _BV(WGM10); // fast PWM 8-bit, turn on oc4c
				TCCR4B = (OCR1_1KHz & 0x7) | _BV(WGM12);
				TCCR4C = 0;
				OCR4C = 0;
				break;

			// Timer 5
			case TIMER5A:
				TCCR5A = (TCCR5A & 0x3C) | _BV(COM5A1) | _BV(WGM10); // fast PWM 8-bit, turn on oc5a
				TCCR5B = (OCR1_1KHz & 0x7) | _BV(WGM12);
				TCCR5C = 0;
				OCR5A = 0;
				break;
			case TIMER5B:
				TCCR5A  = (TCCR5A & 0xCC) | _BV(COM5B1) | _BV(WGM10); // fast PWM 8-bit, turn on oc5b
				TCCR5B = (OCR1_1KHz & 0x7) | _BV(WGM12);
				TCCR5C = 0;
				OCR5B = 0;
				break;
			case TIMER5C:
				TCCR5A  = (TCCR5A & 0xF0) | _BV(COM5C1) | _BV(WGM10); // fast PWM 8-bit, turn on oc5c
				TCCR5B = (OCR1_1KHz & 0x7) | _BV(WGM12);
				TCCR5C = 0;
				OCR5C = 0;
				break;

#endif
			default:
				break;
		}

	}
}

void HexMotorBoard::serial_out(void)
{
#ifdef HEX_MOTOR_DEBUG
	Serial.print("shift 0x");
	Serial.println(ShiftRegister,HEX);
#endif
	digitalWrite(LatchPin,LOW);
	// Output high order bits first
	if (Version>=2)
	{	shiftOut(DataPin,ClockPin, MSBFIRST, highByte(ShiftRegister));
	}
	shiftOut(DataPin,ClockPin, MSBFIRST, lowByte(ShiftRegister));
	// rising edge on latch pin transfers shift register to output register
	digitalWrite(LatchPin, HIGH);
	if (Version==0)
	{   digitalWrite(AdafruitEnablePin, LOW);	// enable output
	}
}

void HexMotorBoard::digitalWrite(uint8_t pin, bool value)
{
	if (pin<0xA0)
	{   ::digitalWrite(pin, value);
		return;
	}
	if (pin==0xFF)	return;	// pin is +5v and can't be changed
	uint16_t pos = (1 << (pin-0xA0));
	bool old_bit = ShiftRegister & pos;
	if ((value && ! old_bit) || (!value && old_bit))
	{   ShiftRegister ^= pos;
		serial_out();
		return;
	}
}

//////////////////////
// AdafruitMotorBoard
//////////////////////

const uint8_t AdafruitDefaultPins[6]={0xFF, 11, 3, 6, 5, 0xFF};

AdafruitMotorBoard::AdafruitMotorBoard(void): HexMotorBoard("-MMMM-",AdafruitDefaultPins,0)
{
}

// Map the motor number to the two control pins for the motors, based on the
// mapping from the AFMotor.h file:
//      MOTOR1_A 2
//      MOTOR1_B 3
//      MOTOR2_A 1
//      MOTOR2_B 4
//      MOTOR3_A 5
//      MOTOR3_B 7
//      MOTOR4_A 0
//      MOTOR4_B 6

const uint8_t AdafruitMotorAPin[5]={0, 1<<2, 1<<1, 1<<5, 1<<0};
const uint8_t AdafruitMotorBPin[5]={0, 1<<3, 1<<4, 1<<7, 1<<6};

void AdafruitMotorBoard::change_motor_bits(uint8_t motor,
										   MotorDir control)
{
    if (MotorMode[motor] != ADAFRUIT) return;	// error
	switch(control)
	{    case FORWARD:
			ShiftRegister |= AdafruitMotorAPin[motor];
			ShiftRegister &= ~AdafruitMotorBPin[motor];
			break;
		case BACKWARD:
			ShiftRegister &= ~AdafruitMotorAPin[motor];
			ShiftRegister |=  AdafruitMotorBPin[motor];
			break;
		case BRAKE:  // set both outputs low
			ShiftRegister &= ~AdafruitMotorAPin[motor];
			ShiftRegister &= ~AdafruitMotorBPin[motor];
			break;
	}
	serial_out();

}

/////////////////////
// HexMotor
/////////////////////

HexMotor::HexMotor(HexMotorBoard &board, uint8_t motor_num)
{
	Board=&board;
	Motor=motor_num;
}

// speed is between -255 (full reverse) and 255 (full forward)
// 0 is off (braking)
void HexMotor::run(int speed)
{
	// clip to legal range
	if (speed>255) speed=255;
	else if (speed<-255) speed= 0-255;
#ifdef HEX_MOTOR_DEBUG
	Serial.print(Motor, DEC);
	Serial.print(" motor running at ");
	Serial.println(speed);
#endif

	switch (Board->MotorMode[Motor])
	{
		case HexMotorBoard::NOT_THERE:
#ifdef HEX_MOTOR_DEBUG
			Serial.print(Motor, DEC);
			Serial.println("motor NOT_THERE. Can't run");
#endif
			return;
		case HexMotorBoard::SIGN_MAG:
			// (Sign-magnitude) IN1 is connected to SIGN, and MAG is assumed to be PWM
			Board->set_signbit(Motor, speed<0);
			analogWrite(Board->SpeedPins[Motor], speed>=0? speed: 0-speed);
			return;
		case HexMotorBoard::ANTIPHASE:
			// (MotorMode) IN1 is connected to MAG, and MAG is PWM
			if (speed==0)
			{   // Brake
				Board->set_signbit(Motor,0);
				analogWrite(Board->SpeedPins[Motor], 0);
				return;
			}
            Board->set_signbit(Motor,1);
			analogWrite(Board->SpeedPins[Motor], (256-speed)>>1);
			return;
		case HexMotorBoard::FORWARD_BACKWARD_BRAKE:
			// (Forward/Backward/Brake) IN1 is connected to MAG, and MAG is ON/OFF only
			if (speed==0)
			{   // Brake
				Board->set_signbit(Motor,0);
				return;
			}
			Board->digitalWrite(Board->SpeedPins[Motor], speed<0);
			Board->set_signbit(Motor,1);
			return;
		case HexMotorBoard::ONE_BIT:
			// IN1 connected to MAG=+5V
			Board->digitalWrite(Board->SpeedPins[Motor], speed<0);
			return;
		case HexMotorBoard::ADAFRUIT:
			// shift_register pins are interpreted differently by Adafruit board
			if (speed>=0)
			{   static_cast<AdafruitMotorBoard*>(Board)->change_motor_bits(Motor,AdafruitMotorBoard::FORWARD);
				analogWrite(Board->SpeedPins[Motor],speed);
			}
			else
			{   static_cast<AdafruitMotorBoard*>(Board)->change_motor_bits(Motor,AdafruitMotorBoard::BACKWARD);
				analogWrite(Board->SpeedPins[Motor],0-speed);
			}
			return;

	}
}

void HexMotor::brake(void)
{
	switch (Board->MotorMode[Motor])
	{   case HexMotorBoard::ADAFRUIT:
			static_cast<AdafruitMotorBoard*>(Board)->change_motor_bits(Motor,AdafruitMotorBoard::BRAKE);
			analogWrite(Board->SpeedPins[Motor],255);
			return;
		case HexMotorBoard::NOT_THERE:
		case HexMotorBoard::ONE_BIT:
#ifdef HEX_MOTOR_DEBUG
			Serial.print(Motor,DEC);
			Serial.println("motor NOT_THERE or ONE_BIT. Can't brake.");
#endif
			return;	// no such operation exists
		default:
			run(0);
			return;
	}
}

void HexMotor::release(void)
{
	switch (Board->MotorMode[Motor])
	{   case HexMotorBoard::ADAFRUIT:
			static_cast<AdafruitMotorBoard*>(Board)->change_motor_bits(Motor,AdafruitMotorBoard::BRAKE);
			analogWrite(Board->SpeedPins[Motor],0);
			return;
		default:
#ifdef HEX_MOTOR_DEBUG
			Serial.println("Not Adafruit motor shield, can't release.");
#endif
			run(0);	// not a release, but a brake on HexMotor boards.
					// The closest the TLE-5206 chips can get.
			return;
	}
}

2011 August 5

Board (partially) populated and tested

My 4-up board about to be cut apart on the board shears. The adjustable railing for the back edge of the board and a railing along the bottom make it fairly easy to line up boards for repeated identical cuts (which I did not need). The bottom rail was useful for making sure that the cut was square, though.

Yesterday, I went to the basement shop where the support team for the enginineering teaching labs have their offices, and used their board shears to cut my PC board up. The shears are like a souped-up paper cutter. The noise they make when cutting through the PC board is a bit scary, though as it it sounds like you are crushing the board, rather than cutting. It makes a pretty clean cut, despite how it sounds.

HexMotor rev1.3 board with one H-bridge installed.

This morning I woke up early and decided to populate the board. I soldered in the switching power supply (and associated resistors and capacitors) first, and checked that there were no shorts and that it produced the correct output voltage. I then added the digital logic, the sockets for connecting to the Arduino, and the various headers.

It turned out that most of the headers did lock in place nicely with the Sparkfun offset-hole header design, making soldering much easier. A few of my 3-pin headers seem to have slightly smaller posts, and they did not lock in place as nicely. The hardest thing to solder in place were the 0.1″ jumper wires (which are not part of the next design). I may want to leave another 1–2 mm for the resistor, also, as I found it a bit difficult to fit the resistor I had into a 5mm spacing. Perhaps I should go with a 7mm spacing.

I only put in one H-bridge for testing, as I did not want to unsolder H-bridges if the board did not work.  If I’d been really careful, I would have waited on the switching regulator as well, since it is not really needed when there are no servos and the Arduino is powered over the USB line.

I spent most of the day writing driver code for the Arduino.  I came up with a pretty simple interface (much simpler than the AFMotor library for the Adafruit motor shield—I may want to extend the library to cover that board as well).

There is one global declaration of a HexMotorBoard to explain how the board is configured. As a minimum, you need to specify for each motor whether it is configured for Antiphase, Sign-Magnitude, or On-Off control. I suppose that if you connected the boards with ribbon cables, you could control several HexMotorBoards from a single Arduino Mega board, though with a standard Arduino there’s not  much point to having more than one HexMotorBoard, as there are only 6 PWM pins (unless you just need  full-on Forward/Backward and brake).

In the setup() procedure, you call the setup() member function of the HexMotorBoard.  To control a motor, you just use a single function: motor_name.run(speed).  The speed is always in the range -256 to 255, with a speed of 0 meaning brake. The software takes care of translating the speed into appropriate commands for the H-bridge, depending on how the H-bridge is jumpered.  (For convenience, I provided an inline function for motor_name.brake() that just expands to motor_name.run(0).)

I couldn’t come up with a much simpler user interface: declare the board, declare each motor, one setup() call for the board, and one function (run) to control each motor.  I suppose that I could get rid of the setup() function, since all it currently does is set the appropriate pins to be output pins and that could be folded into the run() function, but I’ll have to think about the value of keeping the HexMotorBoard::setup() function around to provide a place for consistency checks (like whether the configured pins are capable of PWM output).

Because I’m using the standard analogWrite() and digitalWrite() commands, and not fussing with the PWM frequency, very little code is needed to run on any Arduino.

I tested the board with its single H-bridge using a 12v door-lock actuator, and it worked in all three modes (antiphase, sign-magnitude, and on/off).  I did notice that the TLE-5206 got quite hot when the actuator was run for a few seconds, so I’m definitely going to need a heat sink.  I was planning on using a shared heat sink for the 6 H-bridges, but the electrolytic capacitors get in the way a little.  I’ll make sure to leave more clearance for heat sinks in the next revision.

I don’t have much time over the next few days, but on Sunday I hope to bring the board up to 4 or 6 H-bridges and make and  hook up the heat sink. Hmm—I don’t have any thermal grease—yet another thing to order.

 

 

 

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