I’m working on a customized firmware that is meant to run on RAK3172 modules. However, there is conflicting information on what is actually connected to the HSE32 peripheral on the module:
- RAK3172 Internal Schematic - #2 by beegee and the block diagram in the module’s datasheet suggest it’s a TCXO with power gating via PB0
- The documentation linked in Low Level Development of RAK3172 - #4 by carlrowan suggests it’s a regular crystal, as it specifies disabling TCXO control (i.e. power gating via PB0) and gives specific values for configuring the trimming capacitor banks in the device, which only makes sense for a crystal driven by the internal crystal driver (note that the document linked in that post talks about “LSE” trimming, but that does not make sense as the LSE caps cannot be trimmed and in fact the included files modify
So what is really going on here? What is the correct configuration for the HSE32 block?
All of this would be much easier if you just released the schematics for the RAK3172, please reconsider doing that.