Electel Blogspot

I have previously shown how to use the PIC32 SPI module to use the 12-bit DAC MCP4822: http://electel.blogspot.com/2016/10/pic32-spi-using-mcp4822-12-bit-serial.html . While that does allow you to generate analog outputs as desired, it requires you to use CPU cycles to process the timer interrupt and accordingly drive the SPI module. Since the PIC32 contains DMA channels, the process can be completely offloaded from the CPU. For an idea of the PIC32 DMA module, refer to my previously written article: http://electel.blogspot.com/2016/05/simple-pic32-dma-example.html Fig. 1 - The generated sine wave at fpwm = 400kHz and 32 elements in the sine table So, the simple way of offloading the SPI update to the DMA module would be to let the DMA channel transfer data to the SPI buffer. The SPI module is configured for 16-bit data transfer (since the MCP4822 write command requires 2 bytes). This means that the cell size for the DMA channel has been set to 2 (2 bytes to transfer once triggered). T...

I've been testing the PIC32 DMA recently. The PIC32 has a DMA (direct memory access) module that allows the data transfer in the PIC32 without CPU intervention during data transfer - thus freeing up CPU to perform other tasks while the data is transferred). First, I did a simple test to just see if it works (I've also done some DMA timing testing - I'll talk about them soon in another article). The first test was to just use the DMA module to transfer data from a constant array (from FLASH) to PORTA (LATA for output). This would be visually seen as LEDs connected to PORTA blinking. The code is: //================================ /***************************************************  * Programmer: Syed Tahmid Mahbub  * Target PIC: PIC32MX250F128B  *  * Date: 05/08/2016 - 05/10/2016  *  * Program to test DMA operation  * DMA will transfer const (from FLASH) to PORTA  ***************************************************/ #include "plib.h"  ...