Trainer: Master/CPPM module not working on TX16s

[mha1]

Is there an existing issue for this problem?

• [X] I have searched the existing issues

What part of EdgeTX is the focus of this bug?

Transmitter firmware

Current Behavior

Can't establish Master/CPPM module trainer connection

Expected Behavior

Feeding CPPM signals to the module bay's HB pin as trainer input should work

Steps To Reproduce

• use a receiver capable of outputting CPPM to the module Bay's HB pin
• enable trainer mode Master/CPPM module
• define SF to activate trainer mode
• observe no trainer connection be established

Version

2.9.3

Transmitter

RadioMaster TX16S / TX16SMK2

Operating System (OS)

No response

OS Version

No response

Anything else?

Looking a bit deeper: not a single interrupt for TIM4_CH1 is generated (TIM4_IRQHandler in trainer_driver.cpp) while a valid 8 channel CPPM signal (20ms period, 0.5ms sync) is fed to the HB pin.

My CPPM signal ought to work, right?