How to Use Adafruit PCF8591: Examples, Pinouts, and Specs

The Adafruit PCF8591 is a versatile breakout board featuring the PCF8591 IC, which is a single-chip, single-supply low-power 8-bit CMOS data acquisition device with four analog inputs, one analog output, and a serial I²C-bus interface. This component is commonly used in applications requiring analog-to-digital conversion (ADC) and digital-to-analog conversion (DAC), such as sensor data reading, light intensity measurement, and simple feedback control systems.

• Supply Voltage (VCC): 2.5V to 6V
• Input/Output Voltage (VI/O): 0V to VCC
• Analog Inputs: 4-channel, single-ended or 3-channel differential
• Analog Output: 1-channel, 8-bit resolution
• Resolution: 8-bit for both ADC and DAC
• I²C Address: Selectable via jumpers (0x48 to 0x4F)
• Operating Temperature: -40°C to +85°C

1. Power Supply: Connect VDD to a 2.5V to 6V power source and VSS to ground.
2. I²C Communication: Connect SDA and SCL to your microcontroller's I²C data and clock lines.
3. Analog Inputs: Connect your analog signals to AIN0 through AIN3 as needed.
4. Analog Output: AOUT provides the DAC output, which can be used to control analog devices.
5. Reference Voltage: VREF should be connected to the desired reference voltage for ADC/DAC operations.

• Ensure that the input voltage does not exceed the VCC voltage to prevent damage.
• Use pull-up resistors on the SDA and SCL lines if your microcontroller does not have built-in pull-ups.
• To minimize noise, keep analog signal paths as short as possible and away from high-current traces.
• Configure the I²C address using the onboard jumpers if multiple I²C devices are used on the same bus.

#include <Wire.h>

// PCF8591 default I2C address
const int PCF8591 = 0x48;

void setup() {
  Wire.begin(); // Join I2C bus
  Serial.begin(9600); // Start serial communication at 9600 baud
}

void loop() {
  Wire.beginTransmission(PCF8591); // Start transmission to device 
  Wire.write(0x04); // Control byte - enable DAC, enable ADC0
  Wire.endTransmission(); // End transmission
  
  Wire.requestFrom(PCF8591, 2); // Request 2 bytes from the PCF8591
  Wire.read(); // Read first byte (dummy read)
  int analogValue = Wire.read(); // Read second byte (ADC0 value)
  
  Serial.println(analogValue); // Print the value to the serial monitor
  
  delay(1000); // Wait for 1 second
}

This example initializes the I²C communication and reads the analog value from channel AIN0 every second, then prints it to the serial monitor.

• No response from the device: Check the wiring, especially the I²C connections, and ensure that the correct I²C address is used.
• Inaccurate readings: Verify that VREF is correctly set and that there is no noise in the analog signal path.
• Unable to write to DAC: Ensure that the OS pin is pulled low to enable the output.

• Use a multimeter to check for proper voltage levels at VDD and VREF.
• If using long wires for I²C, consider using a lower pull-up resistor value to maintain signal integrity.
• Check for solder bridges or cold solder joints that might be causing shorts or open circuits.

Q: Can I use this board with a 5V Arduino? A: Yes, the PCF8591 can operate at 5V and is compatible with 5V Arduino boards.

Q: How do I change the I²C address? A: The I²C address can be changed by adjusting the jumpers on the board to one of the eight possible addresses (0x48 to 0x4F).

Q: Can I use differential inputs with this board? A: Yes, the PCF8591 allows for three differential input measurements. Refer to the datasheet for configuring differential inputs.

Q: What is the maximum sampling rate of the ADC? A: The maximum sampling rate depends on the I²C clock frequency but typically is around 100 samples per second.

Remember to always consult the PCF8591 datasheet for detailed information and specifications.