@srgdamiano, thanks talking to me on the phone Wednesday afternoon, explaining to me all your recent advances and successes.
All, I just answered that question on GitHub here: https://github.com/EnviroDIY/ModularSensors/issues/162#issuecomment-459879699
Here it is, also pasted below.
From what I understand, to get the Digi XBee3 LTE-M module to work on the Mayfly with Modular Sensors, it is necessary to:
- Use “Bypass” mode to directly interact with the UBLOX modem chip, bypassing Digi’s chip, rather than using the standard “Transparent” mode, which would cause full freezes (probably due to power instabilities because there isn’t a capacitor chain on the Digi LTE-M module or the Mayfly).
- Turn off the NBIoT radio to speed up the connection, by setting the network technology (“N#) to 2 (LTE-M only).
- Turn off Power Saving mode, because this mode interacts with the network regarding when it will wake again, and if that doesn’t match the logging interval that we give it, it becomes impossible to wake up the modem when we need it.
@SRGDamia1 has implemented these changes in the current develop branch:
She’s had it working since her Jan. 29 commit, be9e2eb, but she’s been working on improvements since then.
This solution still isn’t perfectly stable, because of the following hardware issues (which could all be addressed by an Xbee adaptor shield that I would like to build):
- Neither the Digi XBee3 LTE-M module or the Mayfly have the recommenced capacitor chain on the Xbee power line. This is the likely culprit for brownouts.
- Benefit of optionally switching Xbee-Mayfly pin connections for the “status”, depending on radio module
- The Mayfly doesn’t have a means to separately reboot or power-down the Xbee module
- The Mayfly doesn’t set all the unused pins to Ground, which would be ideal for broader radio compatibility, with for example the Nimblelink Skywire.
The new SODAQ SARA UBEE R410M radio module, https://shop.sodaq.com/sodaq-sara-ubee-r410m.html, has the same UBlox SARA-R410M radio chip as the Digi XBee3 LTE-M module, but it also has a built-in capacitor chain, which could substantially improve the stability when deployed with the Mayfly.
Sara, what did I miss?