Using Direct Memory Access (DMA) on the RP2040 chip #RaspberryPi #RP2040 #DMA

Direct Memory Access (DMA) uses memory controllers separate from the CPU to accelerate data movement between memory locations, or between peripherals and memory. The RP2040 has 12 DMA channels which can stream an aggregate of over 100 megabytes/sec without affecting CPU performance, in many cases.

There are a huge number of options available to set up a DMA transfer. You can think of a DMA channel controller as a separate, programmable processor with the main job of moving data. Memory on the RP2040 is arranged as a bus matrix with separate memory bus control masters for each ARM core and for the DMA system, and several memory bus targets accessed by the masters. Each bus target can be accessed on each machine cycle.

A page for the Cornell University course ECE4760 explains the principles and has code to demonstrate using the DMA capability.

Here we use the DMA subsystem to produce a complete computing system, independent of the main ARM cpus. The DMA machine makes use of memory-copy ability, transport_triggered operations, and self-modifying code. The code consists of a sequence of DMA block descriptors stored in an array. The implemented operations are Turing Complete, and run at about the speed of an Arduino. About 8 million DMA blocks/second can be fetched/executed. There is a history of using only memory-moves to build a general cpu. In 2013 Stephen Dolan published x86 mov is Turing-Complete describing an example of a one-opcode machine. The paper Run-DMA by Michael Rushanan and Stephen Checkoway shows how to do this with one version (Raspbery Pi 2) of ARM DMA. The DMA system on the RP2040 has more transport-triggered functions and is a little easier to build. Joseph Primmer and I built a DMA processor using the Microchip PIC32 DMA system. Addition and branching had to be based on table-lookup. See DMA Weird machine.

See the details here.


Adafruit publishes a wide range of writing and video content, including interviews and reporting on the maker market and the wider technology world. Our standards page is intended as a guide to best practices that Adafruit uses, as well as an outline of the ethical standards Adafruit aspires to. While Adafruit is not an independent journalistic institution, Adafruit strives to be a fair, informative, and positive voice within the community – check it out here: adafruit.com/editorialstandards

Join Adafruit on Mastodon

Adafruit is on Mastodon, join in! adafruit.com/mastodon

Stop breadboarding and soldering – start making immediately! Adafruit’s Circuit Playground is jam-packed with LEDs, sensors, buttons, alligator clip pads and more. Build projects with Circuit Playground in a few minutes with the drag-and-drop MakeCode programming site, learn computer science using the CS Discoveries class on code.org, jump into CircuitPython to learn Python and hardware together, TinyGO, or even use the Arduino IDE. Circuit Playground Express is the newest and best Circuit Playground board, with support for CircuitPython, MakeCode, and Arduino. It has a powerful processor, 10 NeoPixels, mini speaker, InfraRed receive and transmit, two buttons, a switch, 14 alligator clip pads, and lots of sensors: capacitive touch, IR proximity, temperature, light, motion and sound. A whole wide world of electronics and coding is waiting for you, and it fits in the palm of your hand.

Have an amazing project to share? The Electronics Show and Tell is every Wednesday at 7pm ET! To join, head over to YouTube and check out the show’s live chat – we’ll post the link there.

Join us every Wednesday night at 8pm ET for Ask an Engineer!

Join over 36,000+ makers on Adafruit’s Discord channels and be part of the community! http://adafru.it/discord

CircuitPython – The easiest way to program microcontrollers – CircuitPython.org


Maker Business — “Packaging” chips in the US

Wearables — Enclosures help fight body humidity in costumes

Electronics — Transformers: More than meets the eye!

Python for Microcontrollers — Python on Microcontrollers Newsletter: Silicon Labs introduces CircuitPython support, and more! #CircuitPython #Python #micropython @ThePSF @Raspberry_Pi

Adafruit IoT Monthly — Guardian Robot, Weather-wise Umbrella Stand, and more!

Microsoft MakeCode — MakeCode Thank You!

EYE on NPI — Maxim’s Himalaya uSLIC Step-Down Power Module #EyeOnNPI @maximintegrated @digikey

New Products – Adafruit Industries – Makers, hackers, artists, designers and engineers! — #NewProds 7/19/23 Feat. Adafruit Matrix Portal S3 CircuitPython Powered Internet Display!

Get the only spam-free daily newsletter about wearables, running a "maker business", electronic tips and more! Subscribe at AdafruitDaily.com !



No Comments

No comments yet.

Sorry, the comment form is closed at this time.