Using Direct Memory Access (DMA) in STM32 projects #Microcontrollers #Hardware @embedds
Embedds publishes a new article on using Direct Memory Access (DMA) in STM32 projects.
In many microcontroller projects, you need to read and write data. It can be reading data from the peripheral unit like ADC and writing values to RAM. In another case perhaps you need to send chunks of data using SPI. Again you need to read it from RAM and continuously write it to SPI data register and so on. When you do this using the processor, you lose a significant amount of processing time. To avoid occupying CPU, most advanced microcontrollers have a Direct Memory Access (DMA) controller. As its name says – DMA does data transfers between memory locations without the need of CPU.
Every microcontroller architecture has their own way of performing DMA, similar yet setup and use may differ.
Low and medium density ST32 microcontrollers have a single 7 channel DMA unit while high-density devices have two DMA controllers with 12 independent channels. In STM32VLDiscovery their ST32F100RB microcontroller has a single DMA unit having 7 channels.
DMA controller can do automated memory to memory data transfers, and also do peripheral to memory and peripheral to peripheral transfers. DMA channels can be assigned one of four priority level: very high, high, medium, and low. And if two same priority channels are requested at the same time – the lowest number channel gets priority. DMA channel can be configured to transfer data into the circular buffer. So DMA is an ideal solution for any peripheral data stream.
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