This example shows a basic initialization and set up for the AC peripheral. The application monitors an analog input signal, compares it to a fixed voltage and notifies the user via interrupt and an output pin every time the input signal crosses the fixed voltage level. The comparator can be used to monitor battery voltage, or any other DC level.
More details and code examples on the ATMEGA4809 can be found at the following links:
- TB3211 - Getting Started with Analog Comparator (AC)
- ATMEGA4809 Product Page
- ATMEGA4809 Code Examples on GitHub
- ATMEGA4809 Project Examples in START
- Microchip Studio 7.0.2594 or newer (https://www.microchip.com/mplab/microchip-studio)
- ATmega_DFP 2.1.506 or newer Device Pack
- ATMEGA4809 Xplained Pro (ATMEGA4809-XPRO)
The ATMEGA4809 Xplained Pro Development Board is used as test platform.
The following configurations must be made for this project:
- CPU clock frequency is 3.33 MHz
- Configure PD2 as analog input and PA7 as digital output
- VREF
- AC0 voltage reference at 1.5V
- AC0 voltage reference enabled
- AC0
- Positive input - pin 0
- Negative input - DAC voltage reference is used for the negative input
- DAC voltage reference is 0.8 V
- AC0 enabled
- AC0 output enabled
| Pin | Configuration |
|---|---|
| PA7 | AC Output |
| PD2 | AC Input |
-
Connect the board to the PC.
-
Open the atmega4809-getting-started-with-ac-studio.atsln solution in Microchip Studio.
-
Set the Level_Crossing_Detector project as Start Up project. Right click on the project in the Solution Explorer tab and click Set as StartUp Project.
- Build the Level_Crossing_Detector project: right click on the atmega4809-getting-started-with-ac-studio solution and select Build Solution.
- Select the ATMEGA4809 Xplained Pro in the Connected Hardware Tool section of the project settings:
- Right click on the project and click Properties;
- Click on the Tool tab.
- Select the ATMEGA4809 Xplained Pro (click on the SN) in the Selected debugger/programmer section, and Save (CTRL + S):
- Program the project to the board: click on the Debug tab and click Start Without Debugging.
In this demo, the AC output will go high (5V) when the input signal is above the threshold (0.8 V) and low (0V) when the input signal is below the threshold. In the following figures, the green signal is the input signal and the yellow signal is the output of the AC.
Input: sine wave
Input: triangle wave
Input: square wave (20% duty cycle)
Input: square wave (50% duty cycle)
Input: square wave (80% duty cycle)
This project shows a basic configuration for the AC peripheral. The application monitors an analog input signal and compares it to a fixed voltage. An interrupt is triggered and a pin is toggled every time the input signal crosses the fixed voltage level.