RAK4270 TXCO via DIO3

i see RAK4270 documentation and found next text
Set Dio3AsTxcoControl = enable
But on schematics i see than R3 = NC and C35 0R. Can anybody say me about TXCO control via DIO3 ? Need manually soldering R3 and change C35 or some RAK4270 support TXCO control ?

Thanks in advance

Is there a TCXO populated on your board, or is there a 4-pin crystal as the schematic seems to show the default component selections configured for?

See figure 4-2 of the SX1261/2 data sheet

The depicted schematic shows a configuration for an external crystal, with DIO3 not connected to what is basically a ground pin on a crystal; conversely for a TCXO XTB would need be disconnected.

What is your goal here? Are you attempting to write a firmware from scratch, or to modify the module internals by reworking the components?

If a TCXO is fitted and you don’t enable it in software, I don’t think the board is going to work, conversely if you do enable it when it is not fitted, you should seemingly get an XOSC error which will not clear.

My suspicion is that a TCXO is in fact fitted and the circuit and factory code are configured for that, and unless you are seeing excessive current drain in sleep mode, it’s already being correctly controlled. But I could be wrong.

I want change custom software for RAK4270 with minimum consumption.

What evidence suggests the TCXO is not already optimally managed by the state machine built into the radio chip?

What does your custom software do to attempt to achieve the designed low power consumption?

I want to turn off the TXCO to reduce current consumption. I use Semtesn LORAWAN stack, but adapted for my applications. If it is possible to manage the THCO, then why not use this opportunity?

Now RAK4200 is used, but after a small change it will be RAK4270

If a TCXO is present, then at least with how the chip is configured by the factory firmware, it’s already being optimally managed by a state machine in the radio chip itself which keeps it off except for the brief periods of time when it is needed to transmit or check for a downlink.

To do anything beyond what’s already done, you’d have to substantially rework the board by replacing the TCXO with a crystal.

What does your custom firmware command?