Datasheet

• Built-in potentiometer
• I2C bus
• 3.3V and 5V logic compatible.
This module is basically a reference design to show off some possible applications of
the PCF8591 chip. It is a good learning module which incorporates both ADC inputs
and a DAC output and includes basic sensors in a nice small inexpensive package. It
also has some practical use in projects that can make use of the built-in features.
DAC Analog Output
The DAC output is connected to pin AOUT.
The 8-bit single output provides 256 steps of resolution. For a VCC of 5V, the step
size will be 5V/256 = 20mV.
The DAC output has a modest current capability to begin with and also has a 1K
resistor and LED hooked up to it. The LED makes it easy to see the affect of changing
the analog output for experimenting, but for use in actual applications it limits the
output swing from reaching full Vcc. If Vcc is 5V, it will max out at about 4.2V. For
applications that need the full GND to Vcc swing of the DAC output it is
recommended to remove the LED to avoid the extra load on the output.
The DAC is also used internally by the ADC inputs. If using the DAC output, a track-
and-hold circuit keeps the value that was set on the output pin while the DAC circuit
is being used by the ADC circuit.
ADC Analog Inputs
The 4 analog inputs connect to the header pins AIN0-AIN3 and can be used as 4
general purpose analog inputs. By default these are 4 single-ended inputs
referenced to ground. The PCF8591 chip also supports using them as 2 differential
inputs. Refer to the datasheet for specifics on using that mode.
There are 3 jumpers installed on the module that alternatively connects an on-board
LDR, thermistor and potentiometer to 3 of these 4 inputs as follows. If you want to
use those inputs as general purpose inputs, the jumper should be removed from
that location.