Faster Color Graphics: Adafruit_GFX Gains DMA

An experimental feature in the latest Adafruit_GFX library release can improve drawing performance by up to 2.7X in some cases, when using color displays interfaced to SAMD microcontrollers (“M0” and “M4” boards) over SPI.

The update can be installed using the Arduino Library Manager. While you’re there, check for any updates specific to your display type(s), e.g. Adafruit_ILI9341.

This new feature is disabled by default. To switch this on, a line in Adafruit_SPITFT.h (in the Adafruit_GFX directory) must be edited. Remove the initial comment characters so it reads:

#define USE_SPI_DMA ///< If set, use SPI DMA if available

Additionally, the Adafruit_ZeroDMA library must be installed for this to compile. Keep in mind that this works ONLY on SAMD microcontrollers (M0 and M4) using SPI-interfaced color displays. The new code uses a fair chunk of RAM — about 3.2 Kilobytes with a 320×240 pixel screen, but most projects should be able to afford that on these beefier chips.

DMA — direct memory access — is a feature of modern microcontrollers that gives some code the ability to do two or more things at once. The GFX library can’t yet fully benefit from that…not without breaking compatibility with all existing projects…but as a start we can use it to eliminate the inter-byte delays that normally occur in SPI block transfers, and even just that change makes a big difference.

Outlined shapes generally won’t see any change. Filled shapes (circles, triangles, etc.) average about 2X as fast on M0 microcontrollers, 1.5X on M4. But a few…like filled rectangles and screen clears or fills…perform even faster.

It’s just a first step but opens the doors to some other cool stuff we have planned.

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:

Join Adafruit on Mastodon

Adafruit is on Mastodon, join in!

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, 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!

CircuitPython – The easiest way to program microcontrollers –

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 !

No Comments

No comments yet.

Sorry, the comment form is closed at this time.