Spin Stamp Video Problem

Greg Norton

I have constructed a fan controller project using the Spin Stamp that is supposed to output data to a tv. I had this code working on the propeller demo board before I created my PCB, so I'm reasonably sure the code is correct. When using the Spin Stamp and my PCB, I get no video output. My program must be running as it correctly performs other functions (LED control, fan PWM control, etc). I cannot even run the demo program provided with the propeller for video output (my modified version attached). So I have concluded something must be wrong with my circuit or construction. I did find the section of the Spin stamp manual that says I must change my clocking setup to the following:

_xinfreq = 10_000_000
_clkmode = xtal1 + pll8x

I examined the waveforms on the video output using the oscilloscope, but don't know if these are correct or not (see attached). My schematic for the video output was taken directly from Parallax documents, but it's posted here for reference as well. Also, I've attached Does anyone have ideas on what I might be doing wrong?

Any suggestions are appreciated.
Greg

hippy

It all looks reasonably as I'd expect, circuit, code and scope traces. You could try simplifying the test program ...

PUB Main
tv.Start(12)
tv.Str(String("Hello"))

as that should work and remove the possibility something is inadvertently 'hiding' the display; it's there but you cannot see it.

Have you also checked it's not something to do with the TV display or cable ?

Greg Norton

Hippy - I tried your suggestion to make sure the TV display was OK by re-connecting to the demo board. When I returned to my PCB, it started working. It must have been a flaky connection to the TV somewhere along the path.

Thanks.
Greg