Have you fried the chip, with an overvoltage?
Em segunda-feira, 29 de setembro de 2014 05h12min08s UTC-3, Anshuman Rajwar
escreveu:
>
> Hello
>
> I am trying to control an AD7490 16 channel ADC using spi0 on the
> beaglebone black, currently I am using a very simple code where all I want
> to do is get the ADC to read first channel i.e (channel 0) and return the
> value it gets, however it seems that the only two values that AD7490
> returns are 255 and 16. Below is the code I am using
> #!/usr/bin/python
>
> from Adafruit_BBIO.SPI import SPI
> import time
>
>
>
>
> spi = SPI(0,0)
> spi.msh=1000
> spi.open(0,0)
> spi.bpw=16
> keepRunning=True
> n=0
>
> def readVoltages(n):
>
> print("\n"+"talking to the ADC")
> readings=spi.xfer([65535,65535,(2097<<4)])
> print("output from first one"+"\n")
> print(readings)
> print("\n")
> print("I am awake now")
> print("\n")
> readings=spi.xfer([(2097<<4)])
> print("This is what processor gave back "+"\n")
> print(readings)
> print("This is what the reading is "+"\n")
> print(readings[0]&4095)
> print("\n")
> adcOutput=readings[0]&4095
> n+=1
> return adcOutput,readings,n
>
>
> while(keepRunning):
> adcOutput, readings,n=readVoltages(n)
> y_or_n=raw_input("Should I run again??")
> print("\n"+y_or_n)
> if(y_or_n is "n"):
> keepRunning=False
> n+=1;
> print "I finished **********************"
> spi.close()
> Below is my output
>
> talking to the ADC
> output from first one
>
> [255, 255, 16]
>
>
> I am awake now
>
>
> This is what processor gave back
>
> [16]
> This is what the reading is
>
> 16
>
>
> Should I run again??n
>
> n
> I finished **********************
>
> The structure of the control register of AD7490 is below
>
> 11 10 9 8 7 6 5 4
> 3 2 1 0
> WRITE SEQ ADD3 ADD2 ADD1 ADD0 PM1 PM0 SHADOW WEAK/TRI RANGE CODING
>
>
> The word size is 16 bits so when I want to program this ADC to read only
> first channel I send
> 2097<<4. But I always get 16, it does not matter whether I am applying any
> voltage to the ADC or not.
>
> Please help me, its a very simple code and I cant think of a reason that
> it is not working.
>
>
>
>
>
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