UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

Karen O · 6th Jul 2011, 4:09 pm

Hi Dominic,

I am gathering together parts to attempt to generate a TV signal in exactly the way you describe - straight out of the memory and into a video DAC.

I found a (possibly old) copy of the CF spec on the web (which I'm pleased about - the CFA charges $100!) It suggests that reading at around 6 Mbytes/sec as a byte stream is just possible which is good because the 405 line square pixel clock is around that frequency.

I plan to read my CF card in 8 bit PC mode which is frankly not a lot different to IDE mode. That means I can probably modify a CF-IDE adapter and take the eye strain out of the task. My eyes simply aren't good enough for those ridiculous lead pitches any more.

My plan is to get a PIC generating the sync pulses and timing the transfers from card to DAC latch. The PIC is nowhere near fast enough to handle a 6MHz byte stream but it doesn't need to - it just produces read pulses at that rate.

The PIC can talk to the card (slowly) during the frame blanking period and hopefully set up a multi-sector transfer command. Then, when it gets to the active picture lines, it can clock the bytes out. Conveniently, a sector (512 bytes) is conveniently around one scan line (512 bytes @6MHz is 85usec)

I will pre-load the first sectors of my CF card with an image using my Ubuntu machine.

I don't know if it will work but if it doesn't, I won't have invested much.

6th Jul 2011, 4:09 pm	#34
Karen O Rest in Peace Join Date: Jul 2011 Location: Bridgnorth, Shropshire, UK. Posts: 787	Re: Simple memory card player idea Hi Dominic, I am gathering together parts to attempt to generate a TV signal in exactly the way you describe - straight out of the memory and into a video DAC. I found a (possibly old) copy of the CF spec on the web (which I'm pleased about - the CFA charges $100!) It suggests that reading at around 6 Mbytes/sec as a byte stream is just possible which is good because the 405 line square pixel clock is around that frequency. I plan to read my CF card in 8 bit PC mode which is frankly not a lot different to IDE mode. That means I can probably modify a CF-IDE adapter and take the eye strain out of the task. My eyes simply aren't good enough for those ridiculous lead pitches any more. My plan is to get a PIC generating the sync pulses and timing the transfers from card to DAC latch. The PIC is nowhere near fast enough to handle a 6MHz byte stream but it doesn't need to - it just produces read pulses at that rate. The PIC can talk to the card (slowly) during the frame blanking period and hopefully set up a multi-sector transfer command. Then, when it gets to the active picture lines, it can clock the bytes out. Conveniently, a sector (512 bytes) is conveniently around one scan line (512 bytes @6MHz is 85usec) I will pre-load the first sectors of my CF card with an image using my Ubuntu machine. I don't know if it will work but if it doesn't, I won't have invested much.