15Khz (240p) Signal GeneratorApril 3, 2019
This is the firmware used in the Sweet15 device which you can read about here.
The current code was written in BASCOM-AVR, and I used the built in debugger along with a Saleae Logic analyzer to compare the real world output with that of a Super Nintendo. I debugged the tar out of this thing to get the timings hopefully near perfect. You can program the BASCOM code easily onto a ATTINY2313 with the cheap, yet powerful, TL866II Plus.
Here is the code for NTSC, which is a modified version of a great PAL example, a large inspiration for this project, which I found here. Major credits go to this individual (‘Dim’).
When programming the board be sure to remember to upload as INTEL HEX and set fuse settings in the Xgpro software used by the TL866II.
Select INTEL HEX when you open the .hex file you compiled in BASCOM-AVR
For fuse settings, the ATTINY2313 datasheet on page 30 has the settings layed out…
The relevant settings are on the config tab in the software. As we are using a 20MHz external crystal we want CKSEL to be 1111 and SUT as 10 (20Mhz Crystal Osc. w/ fast rising power)
It is important the fuse settings are correct! You can brick your AVR if set incorrectly =[