Timings for drawing VGA graphics

[mwachs5 (Megan A. Wachs)]

Hi Jookia,

There are some other threads on this topic about the GPIO bitbanging frequency, see below.

Your intuition is spot on about how the instruction caching of the scratchpad would work. All instructions are actually cached on the HiFive1 as there is no instruction scratchpad RAM or maskROM for the instruction pipeline (those are all on the data path, shared with the instruction fetch). As long as your code fits in the ICache, it won’t get evicted.

I’m not personally familiar with the specific requirements for driving VGA, but there are lots of LCD / LED screens out there on which one could make a cool Pong game that the HiFive1 would absolutely be capable of driving.

Speed of the E31 at its I/O pins

Hi Jack, I wonder what is the speed of your E31 CPU running at 320MHz at the I/O pins. What is the maximum available toggling frequency on its I/O pins ? We have some fast control applications in mind with your E31. Thanks. Pavel

Fast Methods for Toggling GPIO Pins

This code will toggle the Arduino pins 8 through 13 every ~29ns: int main(int argc, char **argv) { // Set up the GPIOs such that the LED GPIO // can be used as both Inputs and Outputs. const unsigned int mask = 0x3f; GPIO_REG(GPIO_INPUT_EN) &= ~mask; GPIO_REG(GPIO_PULLUP_EN) &= ~mask; GPIO_REG(GPIO_OUTPUT_EN) |= mask; unsigned int base = GPIO_REG(GPIO_OUTPUT_VAL) & ~mask; while(1) { GPIO_REG(GPIO_OUTPUT_VAL) = base; base ^= mask; } return 0; } Any ideas on h…

GPIO Loopback

While learning how the GPIO works I did a quick test of how fast a signal can get between GPIO pins oh the Hifive1 (including through the level shifters). Rough timing is about 0.125us per transition (8,000,000 transitions per second). Really brain-dead code below if anybody is interested - next up it so see how quick it will work using interrupt on change. PS. Don’t forget to add a jumper wire between Digital I/O 8 and Digital I/O 9 - (GPIO0 and GPIO1). #include <stdio.h> #include <stdlib.h>…