What version of iX12 firmware did you do this testing on? I have found a bug in the spektrum transmitter. In the telemetry data you can set pole and ratio. Pole you can change ratio however you can not. Spektrum has confirmed this is a bug. I don’t know at this point if it related to my problem. I have poles set to inhibit but have no way of viewing ratio in the TX.

installed CC cable from spirit telemetry still does not function correctly.

On my Oxy 3 Heli I have a 4S 4100kv motor main gear 140/pinion 14T so 10:1 ratio.
I have a talon 35 ESC normal mode 3800/idle up1 3900/ idle up2 4000. Telemetry data shows 3400rpms and does not change even as I flick through to idle up 2.

On my Trex 450 I see similar results rpms hits an upper limit and then never changes. Either their is a bug in the iX12 or the spirit FBL has something screwy.

Unfortunately we can't check the firmware version as the radio is with our customer. But it was all stock from factory (bought 3 months ago).

Regarding RPM limit, sadly CC has telemetry limitation for approx. 20 000 RPM for motor.
When you will add Gear Ratio you will hit the limit with a smaller models.
The only solution for this is that Castle will change their protocol. You can find the specs online if you are interested in it.
This is not a bug but just technical limitation in the telemetry protocol they have. It will work in the same way with any FBL or other device that has support for this.

The easiest solution is to connect Castle RPM output lead at the PIT pin. Then the RPM is processed by the Spirit unit and there is no limitation. But this lead is not present on each CC ESC.

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Spirit System developer

There was a recent firmware update.

Do you have a link to that spec by chance. You are probably onto something. 3800*10=38000 motor rpms. Which kinda explains why it was working with the slower head speed.

I got a response from CC. I’m posting this here so if others run into the same issue.
Due to bandwidth and processor limitations the Castle Link Live protocol can only report up to 100,000 electrical RPMs. This is a limitation of the communication protocol and we cannot expand this feature in our current generation of products. The maximum mechanical RPM would be dependent on the number of magnetic poles in the motor. We could report up to 100,000 RPM / (Magnetic poles / 2). So for a 10-pole motor the max RPM reading would be 20,000; for a 4-pole it would be 50,000