MCP3208

Arduino library for MCP3208 8 channel, 12 bit, ADC chip

Usage

The library provides a constructor which takes a chip select pin number. To use the library you must first create a new MCP3208 object with the pin number. On the chipKIT boards you also get the option of passing a DSPI object to use a different SPI bus than the default:

Arduino or chipKIT:

MCP3208 myADC(10);

chipKIT only:

DSPI1 mySPI;
MCP3208 myADC(&mySPI, 10);

You can also miss out all parameters and the default chip select pin of 10 will be used.

Reading the ADC values can be done in two ways. The chip supports both normal linear analog reading (as the on-board ADC on Arduino and chipKIT boards provides), and also differential reading; that is the difference between the voltages applied to two adjacent channels.

To do a normal straight reading use the analogRead() member function of the MCP3208 object. For instance, to read from channel 3:

int myValue = myADC.analogRead(3);

For differential reading channels are numbered 0 to 3 instead of 0 to 7 and form the single-ended pairs 0+1, 2+3, 4+5 and 6+7. The analogReadDif() member function is used to read a differential value, so to read the voltage difference between inputs 4 and 5, you would use:

int myValue = myADC.analogReadDif(2);

Differential reading is done in either one or two stages depending on the voltages applied. If the voltage difference is positive then the channels are read simultaneously and the value returned. However, if the difference is negative the first reading will return an invalid value, so the channel assignments are then swapped and a new reading taken. The negative of this new value is then returned, thus giving you the full positive and negative difference ranges.

For more detail on how the chip works you should consult the datasheet:

http://ww1.microchip.com/downloads/en/DeviceDoc/21298c.pdf