Nova 410 why 4 /dev/ttyUSBx ?


#1

Hi,

I’ve been working with the Nova-R410 (attached to an Orange Pi running Armbian Ubuntu) for a week or so. I’ve learned that when the proper driver is installed (automatically when using the Hologram CLI or manually) that four new devices appear:

/dev/ttyUSB0
/dev/ttyUSB1
/dev/ttyUSB2
/dev/ttyUSB3

I am able to open /dev/ttyUSB2 and interact with the Nova–unless a ppp session is established. I am reading that a limitation of the U-Blox SARA R410 is that it supports only one connection at a time, so I can only send it AT commands when it is not in a ppp session.

My questions are:

  1. is it true that I cannot send AT commands while a ppp session is active?
  2. if only one connection to the Nova is supported at a time, where does the driver create 4 /dev/ttyUSBx devices?

All help is greatly appreciated.

Regards,
Matt


#2

So originally I was going to say yes only PPP or AT commands and that is true for an individual interface, (ie one of the ttyUSBX ports) but per the AT command manual

see page 11 https://www.u-blox.com/sites/default/files/SARA-R4-SARA-N4_ATCommands_(UBX-17003787)_0.pdf

SARA-R4 / SARA-N4
u-blox cellular modules can implement more than one interface between the DTE and the DCE, either virtual interfaces (multiplexer channels) or physical interfaces (UART, USB, SPI, etc., when available). Each interface works as specified by the followings definitions. If not differently stated, all the subsequent
descriptions are applicable to each interface

Also in section B.5 on page 295:

u-blox cellular modules support multiple AT command interfaces, that means a certain number of virtual or physical channels that work as described in Definitions. Each interface maintains an own run-time AT commands configuration (AT command profile); …

The USB interface implements multiple AT command interfaces.

So my reading is it may be possible to have multiple virtual interfaces over USB and have one of those interfaces be PPP (Data mode) and one be Command mode.


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