The pin names in the Python code match the signal names on the schematic at http://osepp.com/wp-content/uploads/2013/07/OSEPP_motor_shield_v1-0.pdf.
So, DIR_SER=Arduino.D8, DIR_EN=Arduino.D7, DIR_ CLK=Arduino.D4 and DIR_LATCH=Arduino.D12. When I get round to it, I'm going to replace the motor shield and Beaglebone PWM outputs with a purpose-built daughterboard. I'll use an ATmega328p with a couple of H-bridge drivers controlled via I2C from the BBB. I found that the BBB is too susceptible to noise and motor startup current drain to interface to servos directly. I'll have the BBB and sensors running on separate 3.3V supply from the daughterboard, motors and servos on 5V. Good luck. On Sun, Feb 16, 2014 at 6:24 PM, <[email protected]> wrote: > Hi Morgan, > > How is the Motor shield wired to the beaglebone? I see that you are using > P8_9,10,15, and 16, wondering what pins on the shield are the hooked up to. > > > On Thursday, September 5, 2013 1:29:55 PM UTC-5, T.Morgan wrote: >> >> I'm using an Arduino Motor & Servo >> Shield<http://osepp.com/products/shield-arduino-compatible/motor-servo-shield/>. >> It's obviously not pin compatible, but it's cheap ($20). >> The only fiddly part is controlling the on-board 74595 shift-register. I >> used the following Python script. >> >> >> import Adafruit_BBIO.GPIO as GPIO >> >> # Beaglebone pin names for interface to 74HCT595 latch >> # (Arduino lib name = shield name = BBB pin) >> MOTORENABLE = DIR_EN = "P8_15" >> MOTORDATA = DIR_SER = "P8_16" >> MOTORCLK = DIR_CLK = "P8_9" >> MOTORLATCH = DIR_LATCH = "P8_10" >> >> def bit(n): return 1<<n >> >> class ShiftRegister(object): >> >> def __init__(self, d): >> self.data = d >> GPIO.setup(DIR_EN,GPIO.OUT) >> GPIO.setup(DIR_SER,GPIO.OUT) >> GPIO.setup(DIR_CLK,GPIO.OUT) >> GPIO.setup(DIR_LATCH,GPIO.OUT) >> GPIO.output(DIR_EN,GPIO.LOW) # Enable shift register >> self.transmit() # Switch off (RELEASE) all motors >> >> def string(self): return '{0:08b}'.format(self.data) >> def bit(self, n): return GPIO.HIGH if (self.data & bit(n)) else >> GPIO.LOW >> def set(self, n, x): # Set the nth bit on or off >> if x: >> self.data |= bit(n) >> else: >> self.data &= ~bit(n) >> def setall(self, d): self.data = d >> >> # Copy self.data to the 74HCT595 shift register one bit at a time via >> the >> # serial data bit (DIR_SER). Each time the serial clock (DIR_CLK) >> goes from >> # low to high, the current contents of the 74HCT595's register are >> shited >> # one bit to the left and DIR_SER is copied into the rightmost bit. >> # When DIR_LATCH goes from low to high the contents of the shift >> register >> # are moved to the chip's 8 output pins. >> # (These 8 bits control the motor shield's 4 H-bridges.) >> def transmit(self): >> GPIO.output(DIR_LATCH,GPIO.LOW) # - Set latch trigger low >> GPIO.output(DIR_SER,GPIO.LOW) # - Set serial data bit low >> for i in xrange(0,8): # - For each bit of >> motor_register: >> GPIO.output(DIR_CLK,GPIO.LOW) # - Set serial clock >> trigger low >> GPIO.output(DIR_SER, self.bit(7-i)) # - Copy register >> bit(7-i) to the serial data bit >> GPIO.output(DIR_CLK,GPIO.HIGH) # - Set serial clock >> trigger high; the >> # rising edge shifts the >> serial data bit >> # into the 74HCT595's >> shift register. >> GPIO.output(DIR_LATCH,GPIO.HIGH) # - Set the latch trigger >> high; the >> # rising edge sends the >> stored >> # bits to the 74HCT595's >> parallel outputs. >> GPIO.output(DIR_SER,GPIO.LOW) >> GPIO.output(DIR_CLK,GPIO.LOW) >> GPIO.output(DIR_LATCH,GPIO.LOW) >> >> and call with: >> >> # Shift register bits motor control bits (from AFmotor.h) >> # (Bit positions in the 74HCT595 shift register output.) >> MOTOR1_A = 2 >> MOTOR1_B = 3 >> MOTOR2_A = 1 >> MOTOR2_B = 4 >> MOTOR3_A = 5 >> MOTOR3_B = 7 >> MOTOR4_A = 0 >> MOTOR4_B = 6 >> MOTOR_BITS = [(MOTOR1_A,MOTOR1_B), (MOTOR2_A,MOTOR2_B), >> (MOTOR3_A,MOTOR3_B), (MOTOR4_A,MOTOR4_B)] >> >> # 74HCT595 output bits >> # 7 6 5 4 3 2 1 0 >> # 3B, 4B, 3A, 2B, 1B, 1A, 2A, 4A >> >> class Robot(object): >> >> def __init__(self): >> self.control_bits = shift_register.ShiftRegister(0) >> ... >> >> # Switch motor's control bits depending on command. >> def run(self, motornum, cmd): >> >> # Find the control bits (74HCT595 output pins) corresponding to >> the given motor. >> a, b = MOTOR_BITS[motornum -1] # Arduino library uses 1..4 >> >> # Translate the given command into a pair of control bits >> x, y = COMMAND_BITS[cmd -1] # Arduino library uses 1..4 >> >> self.control_bits.set(a, x) # Set bit MOTORn_A >> self.control_bits.set(b, y) # and bit MOTORn_B. >> self.control_bits.transmit() # Send the control bits to >> the 74HCT595. >> >> -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to a topic in the > Google Groups "BeagleBoard" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/beagleboard/bBNE16rJA5w/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > For more options, visit https://groups.google.com/groups/opt_out. > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. 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