Edit - Grin have gotten back to me on this issue, and tell me the 5v signal on the mains cable should not be affected by the TRS plug - these guys know what they're doing so I don't doubt that information, but for my 2 BR controllers whenever the old TRS cable is plugged in, the 5v to throttle (on the Mains plug) goes to 0v, so no throttle.
If you're having this issue, the info below might solve your problem... or it might not
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Quick post to hopefully help someone else with this issue...
The programming jack on later model Baserunner and Phaserunner controllers uses a 3.5mm TRRS jack, as per the pic below (copied from the Grin website).

BUT earlier model Phaserunner/Baserunner controllers, and the earlier Grin TTL cables used a TRS jack, with just the Tx, Rx and Gnd poles, as per the pic on the left below.

If you're using one of the TRRS equipped controllers with a Cycle Analyst, the early TRS cable will work ok (see note below).
BUT - if you're using the early TRS cable without a CA on a TRRS controller (and providing throttle input via a Mains cable adapter) the TRS plug will short the 5v signal to Gnd (see below), it appears this 5v signal is shared with the throttle 5v at the mains plug, so you wont have a throttle signal while the programming cable is plugged in.

You can still program the controller, or run autotune, but without a 5v supply to the throttle the controller will be unresponsive until you unplug the cable.
If you have an older TTL cable, and want to program the newer controllers (and bench test them with the cable plugged in so you can see the dashboard on the PR suite) you can make an adapter using a female TRS jack, and male TRRS jack, and just leave the 5v pin unterminated.
Note that the older TRS cable works ok if you have a Cycle Analyst on the bike, because the CA provides the 5v signal to the throttle, BUT I don't know whether shorting the 5v to Gnd will do any damage to the controller, maybe someone from Grin can advise on that?
This little issue cost me a few hours of shop time, (and quite a few emails to Grin without resolution), so hopefully this helps someone else out
If you're having this issue, the info below might solve your problem... or it might not
-------------------------------------------------------------------------------------------------------------------------------------
Quick post to hopefully help someone else with this issue...
The programming jack on later model Baserunner and Phaserunner controllers uses a 3.5mm TRRS jack, as per the pic below (copied from the Grin website).

BUT earlier model Phaserunner/Baserunner controllers, and the earlier Grin TTL cables used a TRS jack, with just the Tx, Rx and Gnd poles, as per the pic on the left below.

If you're using one of the TRRS equipped controllers with a Cycle Analyst, the early TRS cable will work ok (see note below).
BUT - if you're using the early TRS cable without a CA on a TRRS controller (and providing throttle input via a Mains cable adapter) the TRS plug will short the 5v signal to Gnd (see below), it appears this 5v signal is shared with the throttle 5v at the mains plug, so you wont have a throttle signal while the programming cable is plugged in.

You can still program the controller, or run autotune, but without a 5v supply to the throttle the controller will be unresponsive until you unplug the cable.
If you have an older TTL cable, and want to program the newer controllers (and bench test them with the cable plugged in so you can see the dashboard on the PR suite) you can make an adapter using a female TRS jack, and male TRRS jack, and just leave the 5v pin unterminated.
Note that the older TRS cable works ok if you have a Cycle Analyst on the bike, because the CA provides the 5v signal to the throttle, BUT I don't know whether shorting the 5v to Gnd will do any damage to the controller, maybe someone from Grin can advise on that?
This little issue cost me a few hours of shop time, (and quite a few emails to Grin without resolution), so hopefully this helps someone else out
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