After implementing the video logic in Verilog, and simulated using Icarus Verilog, I decided tro move to hardware.
For this demo, I'll target the MachXO2 breakout board, that has a MachXO2-7000HE, integrated programmer, USB-UART and most of the pins on pads. It does not have footprints for any of the ports I need, so I will put it on a carrier-board made from a failed project PCB.
In my parts bin, there are a couple of Mach XO2 256 and 640 LUT chips, and the design will easily fit in any of those. The 640-part has some block-RAM that can be used as ROM that is lacking in the 256-part, which means I will probably use the 640-part in the final design.
Before putting the MachXO2-BOB on the carrier and doing some modifications I flashed the on-board chip with my design just to verify that I didn't screw something up.
The only way to see if it was alive was to probe with a scope.
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Notice the proper probe-grounding :)
Indeed, there are sync-signals! V-sync is shown in the picture below, and should be exactly 60 Hz, but is a bit off, depending on the internal oscillator of the Mach XO2.
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Since the screen is blank after reset, there should be no video signal, but as can be seen in the video below, there is a periodic signal. That signal is the cursor blinking. The Apple I did not have a blinking cursor, but I added one, as one of the very few extensions.
Next up is the carrier board. I need to locate suitable ground- and power-points, as well as the VGA-signal-pads on the board.
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