MCP4725_PICO

Table of contents

• Overview
• Examples
• Software
  • API documentation
  • Set Voltage Input code
  • EEPROM
  • Power modes
  • General call method
• Hardware
• Output

Overview

• Name: MCP4725_PICO
• Description:

Library Driver for MCP4725 DAC modules, for Raspberry pi PICO RP2040.

The MCP4725 is a low-power, high accuracy, single channel, 12-bit buffered voltage output Digital-to- Analog Converter (DAC) with nonvolatile memory (EEPROM). Its on-board precision output amplifier allows it to achieve rail-to-rail analog output swing.

• Supports MCP4725 features including EEPROM r/w, Power modes and general call.

• Toolchain

  1. Raspberry pi PICO RP2040
  2. SDK C++, compiler G++ for arm-none-eabi
  3. CMAKE , VScode

Examples

There are eight example files. The example files are in example folder. To build the one you want, edit the Cmaketxt file add_executable(${PROJECT_NAME} section, comment in one example file path and one ONLY.

Path Name	Function
isConnected	Check I2C connection continuously, useful for debugging I2C bus issues
demoTest	Carries out Test on various features, EEPROM, power mode's etc
setVoltage	Carries out Tests on voltage and input code methods
squareWave	Generates a square waveform 100 Hz
triangleWave	Generates a triangle waveform 75 Hz
sawToothWave	Generates a saw tooth waveform 150 Hz
sineWave	Generates a sinusoidal waveform at various values, see file header
random	Random data generation

The example files output Data to the PC serial port using printf, default settings.(baud rate 38400).

Software

API documentation

The API (application programming interface) documentation is at link hosted on github pages and generated by Doxygen.

URL

Set Voltage Input code

The user can set the Voltage output using a voltage or an input code. The input code is calculated using following. Example ::

0. Required voltage output of 1.65 V
1. Voltage reference of 3.3 Volts
2. DAC resolution of 2^12 (4096)
3. The Din or input code would be 2048.

EEPROM

The Device can store a voltage output value and power mode status in its onboard EEPROM. In the event of a software reset or power loss, The device will read EEPROM and restore these settings. If the power supply voltage is less than the POR(Power-On-Reset) thresh- old (VPOR = 2V, typical), all circuits are disabled and there will be no DAC output. . When Vdd increases above Vpor device "resets" and gets data from EEPROM(stored voltage and power on conditions).

Power modes

The device has 4 modes. Normal and 3 power down modes. During the power-down mode, the device draws about 60 nA (typical).

General call method

The general call address (0x00) is for addressing every device connected to the I2C-bus at the same time. This command may potentially cause issues with other slave devices on the I2C bus. The MCP4725 has two possible arguments here , Reset and wakeup. Reset is a software reset and will result in EEPROM values being set. Wakeup is to exit a power down mode and return to normal.

Hardware

Pinout

Pin	Function
OUT	Analog Voltage output of DAC
GND	Ground Reference
SDA	Digital I/O Serial data. Transmits and receives data
SCL	Digital input Serial clock input. Clocks data on SDA
GND	Ground
VDD	Reference + supply voltage 2.7v - 5.5v, In PICO case connect to 3.3v
A0	I2C Address Bit Selection pin (A0 bit)^^

^^This pin can be tied to VSS or VDD, or can be actively driven by the digital logic levels. The logic state of this pin determines what the A0 bit of the I2C address bits should be. The address is also effected by which variant of chip. There are 3 variant's thus 6 choice's of I2C address

The module tested has 2 X 4.7 kOhm pull up resistors on I2C bus and a bypass capacitor. An additional 10 µF capacitor (tantalum) in parallel is also recommended to further attenuate high frequency noise.

Output

Saw tooth waveform.

Sine waveform.