ChibiTerm - OMG! Text on VGA

Projects / ChibiTerm  Original post date: 03/08/2016

This is a quick setup without the video buffer, so only one of the primary colours. I haven't finished debugging the code, but the signals on the logic analyzer seems to be reasonably, so I hooked up the output to my monitor.

80x25 line of text on a 640x400 70Hz screen from a low end STM32F030F4. :)

I forgot to subtract the lower offset and when I do, the code wasn't generating video. Probably out of bound error for the font table look up routine.

The solid block on the right side is a result of the rendering code reading off unused FLASH (0xff).

Here is the breadboard. 4 pin plug on left is SWD for debugging and middle cables is the logic analyzer. The tiny board on left of the STM32F0 breakout board is a 25MHz oscillator.

ChibiTerm prototype with video output

This is the VGA test circuit. I am using a 25MHz oscillator as the clock source as the internal RC oscillator has a bit too much jitter.

VGA test schematic - using oscillators for breadboard

Problem fixed: I simply offset the characters in the text buffer as the font table starts off at character 32 instead of 0.

VGA test - text rendering

I set the video parameters for VGA 640x480 60Hz mode (80x30 characters). The firmware just works. :)

VGA 80x30 mode

Power consumption is 20.5mA with the VGA cable unplugged (i.e. uC alone)
With the VGA cable and displaying the test pattern, it is 24mA.