acl wrote:...have you tried this yet with the original baseband SSTV to 625/VGA ? Regards Chris Lewis
No, there are a few incompatibilities between this demodulator and the MkI up-converter. The only way I could see this being used with the MkI is to use the analogue 'monitoring' output to feed the A-D input of the MkI. This would require adjustment of DC and signal levels - though no big deal. But you lose the advantage of the digital FIR filter with its vastly reduced overshoot on rapid (SSTV?) transitions. Even so, it probably would better than the modified Robot 70 version. It's worth investigating...
If you only require a SSTV-baseband (analogue) video the micro could be replaced with something like a 14-pin PIC16F684. That's also worth looking into, thanks for the idea...
However, the objective is to replace all the complex parallel data/address lines of the MkI with a serial arrangement. As things stand the large 32-pin RAM in the MkI would be replaced with one, maybe two, 8-pin serial RAM chips. The output D-A would also hopefully become a single 8-pin device.
Steve A.