#!/usr/bin/env python from spi import SPI # Set up the SPI dac = SPI(2, 0) dac.mode = 1 # SPI mode 1 dac.bpw = 8 # 8 bits pr word dac.lsbfirst = False # MSB transfers # Calculate the value for the DAC iChop = 2.0 # Current chopping limit (This is the value you can change) vRef = 3.3 # Voltage reference on the DAC rSense = 0.1 # Resistance for the vOut = iChop*5.0*rSense # Calculated voltage out from the DAC (See page 9 in the datasheet for the DAC) dacval = int((vOut*256.0)/vRef) # Update all channels with the value for addr in range(8): byte1 = ((dacval & 0xF0)>>4) + (addr<<4) byte2 = (dacval & 0x0F)<<4 dac.writebytes([byte1, byte2]) # Update all channels dac.writebytes([0xA0, 0xFF]) print "All channels now have vOut = "+str(vOut)+", iChop = "+str(iChop)
