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Joseph Goldin

@TheLion Woo! Thanks so much! I made the changes to my usb-serial file as you mentioned, rebooted, and I'm able to use the serial AT terminal.

I'm now using modem-cmd and sms to interface with the modem from Python.

I still get a usb.core.NoBackendError: No backend available reply error when trying to use the python SDK, and I've troubleshooted that for hours to no avail. Has anyone else had any luck? Hopefully Omega does release docs soon.

In the meantime, the AT command reference for Ublox modems is located here:
https://www.u-blox.com/sites/default/files/u-blox-CEL_ATCommands_(UBX-13002752).pdf
https://www.u-blox.com/sites/default/files/AT-CommandsExamples_AppNote_(UBX-13001820).pdf

Using that you can directly interact with the modem from screen /dev/ttyACM1 or modem-cmd [command].

Joseph Goldin

@Douglas-Kryder Thanks, yeah, hopefully Onion or Hologram can respond with some more info. At this point it seems like all that's missing is the piece that lets the Omega2 communicate with the Hologram board. I posted on the Hologram forums at this thread: https://community.hologram.io/t/onion-omega-cellular-expansion-documentation/1026

Thanks for reminding me to take a closer look at the Nova, I'd written it's Python SDK off before as un-usable without actually trying to install it.

At this point, if I decide I really need a cell modem for this project I'll probably just get a Nova and use a RasPi or something. Or try Hologram's Dash board.

Joseph Goldin

So it looks like the Cellular Expansion is essentially the Nova -- they share the same Ublox SARA-U201 modem.
Specs here:
https://hologram.io/store/nova-global-3g-2g-cellular-modem

I wrote everything below before I hit another brick wall. We need the psutil python package cross-compiled, it won't install via pip, and it's the last package needed before hologram-python will install. So you have to install GCC and Make following the guide here: https://docs.onion.io/omega2-docs/c-compiler-on-omega.html. I've revised the below instructions.

To install the Hologram Python SDK, you have to:

opkg install python python-dev python-distutils python-crypto python-pip
pip install --upgrade pip
pip install --upgrade setuptools
pip install python-sdk-auth
Install GCC and Make (https://docs.onion.io/omega2-docs/c-compiler-on-omega.html)
pip install hologram-python

Make sure you have a USB or SD card mounted and setup as the main storage, or you won't have enough room for everything.

You can then use the SDK as described here:
https://hologram.io/docs/reference/cloud/hologram-cli/
and here
https://hologram.io/docs/reference/cloud/python-sdk/opkg

While this allows you to install and run the python SDK, it doens't actually work. I get an error relating no no available usb backend (see code). Bummer.

root@Omega-32CB:~# hologram modem signal
Traceback (most recent call last):
  File "/usr/bin/hologram", line 167, in <module>
    if __name__ == '__main__': main()
  File "/usr/bin/hologram", line 163, in main
    _command_handlers[command_selected_prefix](args)
  File "/usr/lib/python2.7/site-packages/scripts/hologram_modem.py", line 147, in run_hologram_modem
    _run_handlers[args['command_selected']](args)
  File "/usr/lib/python2.7/site-packages/scripts/hologram_modem.py", line 60, in run_modem_signal
    cloud = CustomCloud(None, enable_inbound=False, network='cellular')
  File "/usr/lib/python2.7/site-packages/Hologram/CustomCloud.py", line 35, in __init__
    network=network)
  File "/usr/lib/python2.7/site-packages/Hologram/Cloud.py", line 36, in __init__
    self.initializeNetwork(network)
  File "/usr/lib/python2.7/site-packages/Hologram/Cloud.py", line 50, in initializeNetwork
    self._networkManager = NetworkManager.NetworkManager(self.event, network)
  File "/usr/lib/python2.7/site-packages/Hologram/Network/NetworkManager.py", line 40, in __init__
    self.network = network
  File "/usr/lib/python2.7/site-packages/Hologram/Network/NetworkManager.py", line 70, in network
    self._network.autodetect_modem()
  File "/usr/lib/python2.7/site-packages/Hologram/Network/Cellular.py", line 47, in autodetect_modem
    dev_devices = self._scan_for_modems()
  File "/usr/lib/python2.7/site-packages/Hologram/Network/Cellular.py", line 114, in _scan_for_modems
    if self._scan_for_modem(modemHandler):
  File "/usr/lib/python2.7/site-packages/Hologram/Network/Cellular.py", line 128, in _scan_for_modem
    dev = usb.core.find(idVendor=vid, idProduct=pid)
  File "/usr/lib/python2.7/site-packages/usb/core.py", line 1263, in find
    raise NoBackendError('No backend available')
usb.core.NoBackendError: No backend available

Joseph Goldin

Any word on this? I have my Cell Expansion as of today but there is absolutely NOTHING from Onion on how to use it.

Joseph Goldin

@Daniel-OBrien I've had really weird issues with the power dock. I can't get it to boot with battery only, most of the time, which I think is a current-draw issue. The Omega will begin to boot and expansions will be powered but then the Omega shuts off mid-boot. I can't run from USB-only unless I'm using a 2.4amp charger, and even that's not guaranteed. I usually NEED a small lipo AND usb for power to work.

Joseph Goldin