The ADC Pi V2.2 is an 8 channel 17 bit analogue to digital converter designed to work with the Raspberry Pi platform. The ADC Pi is based on two Microchip MCP3424 A/D converters each containing 4 analogue inputs with up to 18 bit resolution. The MCP3424 is a delta-sigma A/D converter with low noise differential inputs. We designed the ADC Pi to work as a single ended A/D converter using the internal 2.048V reference voltage with the -V pins tied to ground. A voltage divider on the ADC Pi board brings the input voltage range to a much more useful 0 – 5.06V. In this configuration the sample size is 17 bits for each channel.
The ADC Pi is powered through the host Raspberry Pi using the GPIO port and extended pins on the GPIO connector allow you to stack the ADC Pi along with other expansion boards.
The two MCP3424 A/D converters communicate via i2c to the host Raspberry Pi giving you eight analogue inputs to use. A logic level converter is included on the ADC Pi board giving you a buffered 5V i2c port making it easy to add other I2C devices which operate at 5 volts without damaging the raspberry pi 3.3 volt i2c port. The i2c buffer uses N-channel mosfets with a maximum drain current of 100mA.
Datasheets for the MCP3424 can be found on the technical information tab.
The I2C address bits are selectable using the on-board jumpers. The MCP3424 supports up to 8 different I2C addresses so with two A/D converters on each ADC Pi you can stack up to 4 ADC Pi boards on a single Raspberry Pi giving you 32 ADC inputs.
The MCP3424 contains an on-board 2.048V reference voltage with an input range of ±2.048V differentially (full scale range of 4.096V/PGA). A programmable Gain Amplifier gives the user a selectable gain of x1, x2, x4 or x8 before the analogue to digital conversion takes place.
The data rate for analogue to digital conversions is 3.75 (17 bit), 15 (15 bit), 60 (13 bit) or 240 (11 bit) samples per second. Data rate and resolution can be configured within software using the I2C interface.
Unused inputs should be tied to ground.
ADC Pi V2.1 Address Configuration and Specification (Current Model)
ADC Pi V2 Address Configuration and Specification (Previous Model)
Input Ratings & Specifications
Maximum voltage on ADC inputs: ± 5.0V
Maximum current on i2c port: 100mA.
Click to download schematic PDF.
The Quick2wire lib from https://github.com/quick2wire/quick2wire-python-api allows easy access to the I2C port via Python.
Download demo code for the ADC Pi V2 and ADC Pi V2.1.
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The following tutorials are available for the ADC Pi analogue to digital converter board.