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SX126x 127x interoperability at 500khz

Hi all, I’m testing the SX1276 / 1262 interoperability in different contexts. Using the private sync word, they talk with each other without issues, using a home made driver for the SX1276 chip and Radiolib for SX1262, with the exception of the bandwidth set to 500khz: at this bandwidth the same family chips are still able to talk with each other without issues, but not across different families. Other settings are as follows: CR set t 8, spreading 12, explicit header. I’m doing something wrong or there is some actual issue at 500khz? Thanks.

I have previously testing this with the default private sync word (0x1424). They connected no problems on 500k, SF6/7/8/9, CR4_7/8, and implicit header. As mentioned in the datasheet they did not connect using SF5.

This was actually tested with the sx1276 to sx1262 and LLCC68.

Thank you for the information. I’m using the same sync word (and indeed it works well with the other bandwidths), and the only difference compared to what you reported is that I use explicit headers. I noticed that when at 500khz, actually there is one-way communication, but the packets appear corrupted: I wonder if there is something odd happening with the explicit header, when at 500Khz. The reason of this issue, may be related with the fact that following the datasheet, the SX126x driver sets a special register in order to fix the sensitivity issue of the chip. Maybe this also interacts with other stuff. I’ll investigate more. Thanks.

Antirez,

I am using SX1272 to SX1262 with 500KHz bandwidth and not having issues however I do see reduced sensitivity between radio families as opposed to SX1272 to SX1272 as an example with all other radio settings the same. I’m curious about your commend regarding the SX126x driver setting a special register in order to fix the sensitivity issue of the chip. Could you provide more information on this as I am now aware of this. Thank you.

The sensitivity degradation of the SX1216x at 500khz bandwidth is mentioned in the device datasheet.

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Hey Gregg,

Are you seeing similar difference to what I am experiencing below?

SX1276 to SX1276 is fine. But any combination with the LCC68 or SX1262 and there is a decrease in sensitivity.

Hello.

I am still looking into this and there are other forum posts that have helped me zero into this more. I am using CAD and I am starting to believe that with CAD the receiver “locks” up on weaker signals making me think I have a sensitivity issue. I can see CAD is still running and that it is detecting preamble or data but never getting a valid packet. If I reset the radio once I get into this mode I start receiving again. I don’t currently have a clean way to do this without causing other issues but still looking into it further.