Does the 5 byte nRF24LU1+ CHIP ID follow any rules?

[Ed]

I would like to be able to do a sanity check on the CHIP ID.

The Product specification states: "No ID will violate the rules specified in section 6.4.3.2"

Section 6.4.3.2 only states: "Note: Addresses where the level shifts only one time (that is, 000FFFFFFF) can often be detected in noise and can give a false detection, which may give a raised Packet-Error-Rate. Addresses as a continuation of the preamble (hi-low toggling) raises the Packet-Error-Rate."

That does not promise that even that recommendation is actually followed in the CHIP ID.

So: Is the factory pseudo-random CHIP ID byte at address 0x0B in the InfoPage restricted from having an upper nybble of 0xA or 0x5? Or at least not have the values 0xAA or 0x55?

Is it guaranteed that not all the bytes will be the same?

Is it guaranteed that all the suggestions in www.nordicsemi.com/.../How-to-choose-an-address will be followed?

In other words is it just random, or selectively random so that it's always a "good" usable over-the-air address?

If it's not completely random, PRECISELY what are the rules?

Ed

[Håkon Alseth]

Hi Ed,

The first byte going over-the-air (which is the LSByte inputted) will not be 0x00/0xFF/0xAA/0x55. The rest of the content is randomized, which means that you can get into a situation where all bytes are equal (all 0x37 for instance). The chance for this is very low.

Cheers, Håkon

[Ed]

I see. So somewhere out in the world there will potentially be 252 units that simply don't work with Gazelle.

And just to be completely clear, the first byte over-the-air is the one found in InfoPage address 0x0B?

[Håkon Alseth]

You can choose to use this identifier as an address, but it does not mean that you have to. If you use an address like this: {0xc4, 0xc5, 0xc6, 0xc7, 0xc8}, the first byte going over the air will be the 0xc8.