[Paul Stoffregen], known as father of the Teensy, has leveraged the Teensy 3.1’s hardware to obtain some serious speed gains with SPI driven TFT LCDs. Low cost serial TFT LCDs have become commonplace these days. Many of us have used Adafruit’s TFT LCD library to drive these displays on an Arduino. The Adafruit library gives us a simple API to work with these LCDs, and saves us from having to learn the intricacies of various driver chips.
[Paul] has turbocharged the library by using hardware available on Teensy 3.1’s 32 Freescale Kinetis K20 microcontroller. The first bump is raw speed. The Arduino’s ATmega328 can drive the SPI bus at 8MHz, while the Teensy’s Kinetis can ramp things up to 24MHz.
Speed isn’t everything though. [Paul] also used the Freescale’s 4 level FIFO to buffer transfers. By using a “Write first, then block until the FIFO isn’t full” algorithm, [Paul] ensured that new data always gets to the LCD as fast as possible.
Another huge bump was SPI chip select. The Kinetis can drive up to 5 SPI chip select pins from hardware. The ATmega328 doesn’t support chip selects. so they must be implemented with GPIO pins, which takes even more time.
The final result is rather impressive. Click past the break to see the ATmega based Arduno race against the Kinetis K20 powered Teensy 3.1.
Paul’s library is open source and available on Github.
Filed under: Microcontrollers