Non-existing registers

[Haismd03]

Hi, while working on a project I've taken closer look to how this library work.
I've compared register addresses with RFM96W datasheet and found out something I dont understand.

Register address is set to 0x39
#define REG_SYNC_WORD 0x39
The setSyncWord() uses writeRegister that does bitwise OR with 0x80 and then a actually writes to resulted address 0xB9.
This address is actally way beyond last register of RFM96W.

In datasheet, sync word register is only available in FSK/OOK mode. But this library works with LoRaTM. But yet, somehow it does the thing.

Can somebody tell me, how this library works?

[morganrallen]

Not sure where you're getting some of this info from but SyncWord in fact only works in LoRa mode, not FSK.

0x80 in this case is the Write Enable Bit, actual register addresses are only 7-bit. This is briefly described in section 4.3 SPI Interface

The first byte is the address byte. It is comprises:
* A wnr bit, which is 1 for write access and 0 for read access.
* Then 7 bits of address, MSB first.

Hope this clears things up.

[Haismd03]

Thank you @morganrallen for clarification.
It's actually quite interesting, because it seem that I've been using wrong datasheet all the time.
In shop, where I've bought my RFM96W is pinned this datasheet. It's clearly an older version, it's marked as v1.0.

In this version of datasheet, SyncWordConfig register has address 0x27 for FSK/OOK and is actually reserved for LoRa mode.

This is the reason why I was wrong about it. I'll notify admins of this e-shop about this issue.

Also thank you for notifiing me on section 4.3 SPI Interface. I'll take closer look on it.