Classic PTT Issue ?

[Graeme Hendry]

Classic PTT issue, got my DigiPi Hat all up and running, rx fine, catching APRS, but if I add the PTT line the radio keys instantly. 

Guessing I need to reverse the PTT polarity ? where is best to do that, 

I've reimaged a few times through experimenting to not much success  

Yep, if I ground the PTT manually, it keys the radio, so I reckon the cable is fine. 

Radio is a cheap BAOJIE BJ-218 but works fine otherwise. 

Cheers Graeme

[Graeme Hendry]

Just to add

It seems to do this from booting the Pi, not just when Direwolf runs ?

[Craig]

Hi Graeme,  

That's one of two classic PTT issues,

1) PTT stuck-on first transmit (RF on USB cable, add ferrites)
2) PTT engages 20 seconds into boot cycle GPS service thinks your rig is a GPS and is raising the RTS signal

I suspect you have #2.

either change the GPS device in /etc/default/gpsd, or disable gpsd (systemctl disable gpsd; systemctl disable gpsd-socket)

During your next Initialize, be mindful of the GPS device name as well.


cool,
-craig
KM6LYW

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[Graeme Hendry]

Thanks

Done the above, with no change.

Seems to be about 2 seconds after applying pi power, so I don't even think its a digipi issue to be honest.

pins 1 and 2 on the 9  pin D socket of the DigiPi Hat are grounded straight away, pulling the PTT to ground.

I'd be convinced it was the cable if it didn't test fine, and do the PTT thing when manually grounded.

:)

[Craig]

Transmit with power-on would suggest a dead FET on the board, they fail
in the closed position
in my experience.  it could be spurious voltage on the center pin of the
FET too.  There is
an RTS led on the board, i'm curious if it's lit up.

sux, but i think that's a hardware issue.

[Craig]

quick correction, the Hat uses DTR, not RTS, but that doesn't change anything ,just fyi,
-craig

[Graeme Hendry]

Yep 

Have Orange LED is on with power

RED LED comes on when I tell DigiPi to send position

[Craig]

Okay, great information, thanks.  We're looking at a hardware error on the Hat, rig, or somewhere
in cables.   You might email ampear about what you're seeing, maybe he has something we
can test directly on the hdardware.  If DigiPi can toggle that led, the software did the best it
can do.

-craig
KM6LYW

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[Graeme Hendry]

Yeah

I've reached out a few times.

Not had a reply yet.

I will get the meter out and look for shorts.

Cheers