1.4 AFEC with DMA
This example uses AFEC peripheral Library to sample multiple ADC channels using DMA striding.
Description
This example takes 100 samples of three analog inputs at a 5 kHz sampling rate in triggered conversion mode and then sort the data by an analog channel using XDMAC.
Conversion of the three analog inputs (AD0, AD5, AD6) is triggered by the TC peripheral every 200 us. The ADC results are copied to buffer using DMA. Data striding feature of XDMAC is used to store the ADC results by analog channel number. The console displays the ADC results of all the three channels.
Downloading and Building the Application
To clone or download this application from Github, go to the main page of this repository and then click Clone button to clone this repository or download as zip file. This content can also be downloaded using content manager by following these instructions.
Path of the application within the repository is apps/afec/afec_dma_striding/firmware.
To build the application, refer to the following table and open the project using its IDE.
| Project Name | Description |
|---|---|
| pic32cz_ca70_curiosity_ultra.X | MPLABX project for PIC32CZ CA70 Curiosity Ultra Development Kit |
Setting Up the Hardware
The following table shows the target hardware for the application projects.
| Project Name | Description |
|---|---|
| pic32cz_ca70_curiosity_ultra.X | PIC32CZ CA70 Curiosity Ultra Development Kit |
Setting Up PIC32CZ CA70 Ultra Curiosity Development Kit
- Analog input (AD0) is fed from DAC output. Sine wave output is generated on
the DAC output using 100 point lookup table.
- Analog input "AD0" is mapped to Port Pin "PB1" that is routed to "Pin 14 of the EXT1 header"
- DAC output "DAC0" is mapped to Port Pin "PB13" that is routed to "Pin 8 of the EXT2 header"
- Use jumper wire to Connect "Pin 14 of the EXT1" to "Pin 8 of the EXT2"
- Analog input (AD5) is connected to Vcc, or the user can supply input from an
external source
- Analog input "AD5" is mapped to Port Pin "PC30" that is routed to "Pin 6 of J403 header"
- Use a jumper wire to connect "Pin 6 of J403" to Vcc or an external voltage source
- Analog input (AD6) is connected to GND, or the user can supply input from an
external source
- Analog input (AD6) is mapped to Port Pin "PC31" that is routed to "Pin 2 of J403 header"
- Use a jumper wire to connect "Pin 2 of J403" to GND or an external voltage source
- Connect 3.3V from pin 4 of J401 to VREFIN pin on J302. This generates 2.048V reference voltage (VREFP) for the DAC.
- Connect GND from pin 6 of J401 to GND pin on J302.
- Connect the Debug USB port on the board to the computer using a micro USB cable
Running the Application
- Open the Terminal application (Ex.:Tera term) on the computer
- Connect to the PICkit4 On Board
Virtual COM port and configure the serial settings as follows:
- Baud : 115200
- Data : 8 Bits
- Parity : None
- Stop : 1 Bit
- Flow Control : None
- Build and Program the project using its respective IDE
- Console displays 100 samples of the ADC count and the respective input voltages for all three channels
- Note that the VREFP for both DAC and AFEC modules is 2.048V. As a result, the
DAC and AFEC output will saturate at 2.048V.
