MCP3201 ADC accuracy found about 0.4%

Now I have used Excel to calculate the series resistor for Zener voltage reference, and the expected binary value for analog input voltages 2.85V and 2.44V.

Then I used the test function to find the MCP3201 ADC results, as listed below.  I found the accuracy is roughly 8 bits, which is equivalent to 1/256 or 0.4%, which I think is very good.




*** MCP3201 ADC results - tlfong01 2013may06 ***

0V    000 0000 0000 0000 0
3V3   000 1111 1111 1100 0

2V85  000 1101 1110 1001 0
Excel     1101 1111 1101

2V44  000 1011 1111 0010 1
Excel     1011 1111 1010

0V

ADC output byte 1 =  00000000
ADC output byte 2 =  00000000

3V3 

ADC output byte 1 =  00011111
ADC output byte 2 =  11111000

2V85

ADC output byte 1 =  11011011
ADC output byte 2 =  11100111

2V44

ADC output byte 1 =  00010111
ADC output byte 2 =  11100101

pi@raspberrypi ~/python_programs/test_guzuntypi $ sudo python fl2067.py
fl2067.py:268: RuntimeWarning: This channel is already in use, continuing anyway.  Use GPIO.setwarnings(False) to disable warnings.
  setupOutputPin = lambda oPin: GPIO.setup(oPin, GPIO.OUT) # set GPIO pin as output
fl2067.py:270: RuntimeWarning: This channel is already in use, continuing anyway.  Use GPIO.setwarnings(False) to disable warnings.
  setupInputPinWithPullUp = lambda iPin: GPIO.setup(iPin, GPIO.IN, pull_up_down=GPIO.PUD_UP) # set GPIO pin as input, with pull up

*** Start Program - MCP3201 ADC 01   ***


*** Start testing MCP3201 ADC ***

ADC output byte 1 =  00000000
ADC output byte 2 =  00000000

*** Stop testing MCP3201 ***


*** Stop Program ***

pi@raspberrypi ~/python_programs/test_guzuntypi $ sudo python fl2067.py

*** Start Program - MCP3201 ADC 01   ***


*** Start testing MCP3201 ADC ***

ADC output byte 1 =  00011111
ADC output byte 2 =  11111000

*** Stop testing MCP3201 ***


*** Stop Program ***

pi@raspberrypi ~/python_programs/test_guzuntypi $ sudo python fl2067.py

*** Start Program - MCP3201 ADC 01   ***


*** Start testing MCP3201 ADC ***

ADC output byte 1 =  11011011
ADC output byte 2 =  11100111

*** Stop testing MCP3201 ***


*** Stop Program ***

pi@raspberrypi ~/python_programs/test_guzuntypi $ sudo python fl2067.py

*** Start Program - MCP3201 ADC 01   ***


*** Start testing MCP3201 ADC ***

ADC output byte 1 =  00010111
ADC output byte 2 =  11100101

*** Stop testing MCP3201 ***


*** Stop Program ***

pi@raspberrypi ~/python_programs/test_guzuntypi $ date
Mon May  6 02:58:34 UTC 2013
pi@raspberrypi ~/python_programs/test_guzuntypi $

*** Start Program - MCP3201 ADC 01   ***


*** Start testing MCP3201 ADC ***

ADC output byte 1 =  00011011
ADC output byte 2 =  11010010

*** Stop testing MCP3201 ***


*** Stop Program ***

.END