LS7366R.py

#!/usr/bin/python

#Python library to interface with the chip LS7366R for the Raspberry Pi
#Written by Federico Bolanos
#Last Edit: February 8th 2016
#Reason: Refactoring some names

import spidev
from time import sleep


# Usage: import LS7366R then create an object by calling enc = LS7366R(CSX, CLK, BTMD)
# CSX is either CE0 or CE1, CLK is the speed, BTMD is the bytemode 1-4 the resolution of your counter.
# example: lever.Encoder(0, 1000000, 4)
# These are the values I normally use.

class LS7366R():

    #-------------------------------------------
    # Constants

    #   Commands
    CLEAR_COUNTER = 0x20
    CLEAR_STATUS = 0x30
    READ_COUNTER = 0x60
    READ_STATUS = 0x70
    WRITE_MODE0 = 0x88
    WRITE_MODE1 = 0x90

    #   Modes
    FOURX_COUNT = 0x03

    FOURBYTE_COUNTER = 0x00
    THREEBYTE_COUNTER = 0x01
    TWOBYTE_COUNTER = 0x02
    ONEBYTE_COUNTER = 0x03

    BYTE_MODE = [ONEBYTE_COUNTER, TWOBYTE_COUNTER, THREEBYTE_COUNTER, FOURBYTE_COUNTER]

    #   Values
    max_val = 4294967295
    
    # Global Variables

    counterSize = 4 #Default 4
    
    #----------------------------------------------
    # Constructor

    def __init__(self, CSX, CLK, BTMD):
        self.counterSize = BTMD #Sets the byte mode that will be used


        self.spi = spidev.SpiDev() #Initialize object
        self.spi.open(0, CSX) #Which CS line will be used
        self.spi.max_speed_hz = CLK #Speed of clk (modifies speed transaction) 

        #Init the Encoder
        print 'Clearing Encoder CS%s\'s Count...\t' % (str(CSX)), self.clearCounter()
        print 'Clearing Encoder CS%s\'s Status..\t' % (str(CSX)), self.clearStatus()

        self.spi.xfer2([self.WRITE_MODE0, self.FOURX_COUNT])
        
        sleep(.1) #Rest
        
        self.spi.xfer2([self.WRITE_MODE1, self.BYTE_MODE[self.counterSize-1]])

    def close(self):
        self.spi.close()

    def clearCounter(self):
        self.spi.xfer2([self.CLEAR_COUNTER])

        return '[DONE]'

    def clearStatus(self):
        self.spi.xfer2([self.CLEAR_STATUS])

        return '[DONE]'

    def readCounter(self):
        readTransaction = [self.READ_COUNTER]

        for i in range(self.counterSize):
            readTransaction.append(0)
            
        data = self.spi.xfer2(readTransaction)

        EncoderCount = 0
        for i in range(self.counterSize):
            EncoderCount = (EncoderCount << 8) + data[i+1]

        if data[1] != 255:    
            return EncoderCount
        else:
            return (EncoderCount - (self.max_val+1))  
        
    def readStatus(self):
        data = self.spi.xfer2([self.READ_STATUS, 0xFF])
        
        return data[1]


if __name__ == "__main__":
    from time import sleep
    
    encoder = LS7366R(1, 1000000, 4)
    try:
        while True:
            print "Encoder count: ", encoder.readCounter(), " Press CTRL-C to terminate test program."
            sleep(0.2)
    except KeyboardInterrupt:
        encoder.close()
        print "All done, bye bois."