Boron 2G/3G NRF to Ublox UART interface

Hardware
1

I have a Boron 2G/3G that i am programming from scratch (no particle software) but am stuck getting the connection between the nrf52840 and the SARA U201 working.

I have two particular questions that I hope someone can help with.

  1. Should I expect the uart baud rate to be 115200 (factory default) or 921600 (as used in particle firmware)?

  2. Is there a way to enable DTR (drive it low) which is what I think the modem needs to work? I cannot see how to do this from the schematic but is required as described in the Ublox system integration manual.

Thanks

2

If you’re going to bypass the Particle system firmware, you’re kind of on your own. However the baud rate on the U201 starts out at 115200, then is changed to a higher baud rate.

The modem uses hardware flow control, so you’ll need to initialize the RTS1 pin as output and initialize the serial port with hardware flow control enabled.

2 Likes
3

Yes I realise that writing my own firmware puts me out in no mans land, but the Boron hardware is compellingly nice and I just want a simple MQTT client.

I have set RTS to active-low and am pretty sure my uart code is OK as it is also running a serial CLI.

I remain concerned that leaving DTR floating is a possible problem for me.

Thanks

4

Hi @abstractsig,

Any news with this? I’m interested on this as well. Have you publish your results or your code in some place?

Thank you,

Manuel Montenegro

5

Did you manage to do it?

6

No.

but this dude might have