g8gtz wrote: ↑
Fri Jul 06, 2018 9:17 am
It can and sounds a better idea but it's not documented anywhere (ideally on the wiki) so no-one including me knows about it!
OK - I did mention it a while back in the lock lights thread, viewtopic.php?f=15&t=4489&hilit=lock+lights
My lock indicator was a blue LED. Blue LEDs make useful logic line status indicators when connected between ground (or VCC) and logic pins via 1.3k resistors. Blue LEDs will only light above about 2.5V. The current will be low enough due to the 1.3k resistor and the LED threshold to not fry the gate. (OK, probably not fry the gate). As the LED threshold is 2.5V, this will still be seen as a logic high in following gates even if the LED drags down the volts. This is of course just for testing, the logic lines should always be properly buffered rather than have LEDs stuck to them. None of us ever hack signals like this.
I would recommend reading the SERIT FTS-4335 data sheet before doing any modifications. There is a lot of information in there, including descriptions of each pin function (and for Yorkshire ex-pats, even which pin is which)
I found the most useful control lines to monitor for status indicators are TS_VALID and TS_ERROR. It depends which NIM you have but for the SERIT these are found on pins 15, 17, 35 and 37. The lower numbers are for TS1, the higher for TS2. The BATC V2 board uses TS2, so TS2-VALID is pin 35 and TS2_ERROR is pin 37.
TS_VALID indicates when there is a valid transport stream. An LED connected to the TS_VALID signal is effectively a lock light and buffering the TS_VALID signal would perhaps be useful to control a stream or repeater.
TS_ERROR goes high if the TS error rate is too high. It doesn’t go high until a TS is detected and then errors, but unfortunately it will then stay high even if the signal disappears, which makes it less useful. I have not quite figured out how to use that logic yet. Perhaps it is useful in a repeater as a quality indicator to show where the signal is dropping in and out.
Buffering logic signals is beyond the scope of this, but some ideas are here http://hyperphysics.phy-astr.gsu.edu/hb ... uffer.html
Edit - presumably this could also apply to other receivers using NIMs.