CC1352R: SimpleLink LRM changing Spreading Code possible?

I have the same question. I'm using a CC1352P using the 2.5 Kbps Long Range DSSS mode. My application doesn't require the performance of 2.5 Kbps. I only need to wake-up another radio in a very a-periodic method. So I would rather trade off bit-rate for distance. I remember the CC1310 had a 300 baud long range mode. Is there any app-note or recommendations to further increase the range?

I did a quick test with the Launchxl-cc1352P1 boards and a nice whip antenna. The units are separated by about 4 feet.

5 Kbps Simplelink Long Range mode (20 Kchips/second, 2-GFSK, FED r=1/2 k=7, DSSS SF= 2, Tx dev: 5 KHz)

Switching to the  2.5 Kbps Simplelink Long Range mode (20 Kchips/second, 2-GFSK, FED r=1/2 k=7, DSSS SF= 4, Tx dev: 5 KHz)

Moving to the slower speed, increases the RSSI by 1.8 to 2.6 dBm. Which is significant. It would be great if we could increase the DSSS to 8.

Hi Nick,

We have a similar situation here, were we only need a few bytes to be transferred from time to time, but over quite a long distance. Hence, your question is also interesting for our project. But I think at this point, we are talking (maybe) about two different things.

There are two parameters to tweak:
(I hope I can reflect the theory correctly)

- Spreading Factor
- Spreading Code

The spreading factor (SF) is the factor with which the payload is 'multiplied' to increase the signal's bit rate and consequentially increase its bandwidth. E.g. one bit is converted to a 4 bit symbol. We then talk about a spreading factor of 4. AFAIK a maximum SF of 8 is possible with the CC1352 family.

The spreading code is the pseudo noise code (called PN, a sequence of some bits) which replaces each payload/user data unit (like one bit gets one PN sequence) to produce a new symbol called "chip". The bit rate afterwards is SF-times higher than the original information bit rate. Quite often Barker Codes are used as PNs, as they are good detected in the noise.

By choosing different PNs, you can a) protect data from be discovered in the spoectrum by others and b) increase the interference robustness agains other systems even if they are using the same type of modulation and the same frequency.

I don't know which codes the CC13xx's are using. And if they can be redefined/changed would be interesting. That would be my question to be more exact.

Please take a look at:

For the SLR (not Legacy LR) this is also valid for the CC13x2 devices.

Note that when changing spreading factor, this is done by changing the following override on CC13x0:

HW_REG_OVERRIDE(0x505C,0xXXXX)

while on CC13x2, you should use

HW_REG_OVERRIDE(0x5068,0xXXXX)

BR

Siri

Siri sent some documentation (see below).

According to this, you could tweak one register to to SF 8:

HW_REG_OVERRIDE(0x505C,0x073C)

Page 9, swra642.pdf

Thanks for the interesting document, Siri!

We now know how to change the spreading factor, but still not if and how we can change the spreading code.

According to Page 4, Table1, SWRA642 the actually used spreading code for 8 in LRM is:

1 is mapped to ‘11001100’

0 is mapped to ‘00110011’

For example we would like to try the complementary sequence

11100100 and 00011011

Is it possible to change that map?