SX1280 CAD parameters

[GusBon]

Hello,

In a near future I will be developing P2P communication system using LoRa in the 2.4 GHz band.
For this system I plan to use the CAD mechanism offered by the SX1280.
From what is written in https://github.com/jgromes/RadioLib/wiki/Default-configuration, if I use RadioLib I will be forced to use CAD with 8 symbols of sampling ?

If yes, is there a choice motivating this parameter to be inaccessible ? (Like maintaining a kind of homogeneity with the other usable radio chips of RadioLib ?)
If I wanted to use CAD with other parameters, would it be hard to modify the lib to do so ?

Thanks for this great lib and your implication.
gus

[jgromes]

if I use RadioLib I will be forced to use CAD with 8 symbols of sampling ?

The page you refer to is talking about the default configuration of the transmitted packets. In other words, if you call the begin method without arguments, those will be the defualts. However this is not applicable to CAD, which requires more configuration. This is accessible via the library API, both for the blocking as well as the interrupt variants:

RadioLib/src/modules/SX128x/SX128x.h

Lines 466 to 471 in a7f321f

	/*!
	\brief Performs scan for LoRa transmission in the current channel. Detects both preamble and payload.
	\param config CAD configuration structure.
	\returns \ref status_codes
	*/
	int16_t scanChannel(const ChannelScanConfig_t &config) override;

[GusBon]

Thanks for your reply.

So if I call the begin method it will by default use 8 symbols when I call the scanChannel() function of the API.
But if I want to use a different CAD parameter I need to pass the struct with the parameters I want.

The inaccessible mention means that I can't initiate my radio chip with a different parameter ? (I just want to understand, this is not a problem for my application)

I see that the struct have an entry named:

RadioLib/src/protocols/PhysicalLayer/PhysicalLayer.h

Lines 139 to 140 in a7f321f

	/*! \brief Exit mode after signal detection is complete - module-specific value */
	uint8_t exitMode;

But I guess that for the SX1280 this entry is not used as the chip goes back to standby mode every time after a CAD ? (Otherwise I need to read deeper the datasheet...)

[jgromes]

But if I want to use a different CAD parameter I need to pass the struct with the parameters I want

That is correct.

But I guess that for the SX1280 this entry is not used as the chip goes back to standby mode every time after a CAD ?

Indeed, unfortunately the SX1280 CAD is rather limited as compared to SX126x or others, so the only configuration parameter that will actually have any impact is the number of symbols. Keep in mind the value has to be one of RADIOLIB_SX128X_CAD_ON_X_SYMB, for example RADIOLIB_SX128X_CAD_ON_16_SYMB