Support for Nova on a different Linux SBC

[scobb]

We are looking to use the Hologram Nova on a Linux SBC not in the supported hardware list. The device is described at: ReachTech.com.

Besides getting PPP into the kernel build, what other support do we need from you folks? We would simply be using ftp to transfer files. What other secret sauce do you provide?

[mbrenner]

Hi @scobb,

I am also using a SBC. In my case, it’s the Orange Pi (similar to Rasberry Pi). I’m running Ubuntu with Armbian. For connectivity I also set up a PPP connection. As you indicate, you will need necessary PPP support including the PPP daemon.

Beyond that, it will depend on what you want to do. For example, I don’t use the Hologram libraries, so I don’t need to install Python. I also contact specific servers using their IP addresses, so I don’t need DNS lookups.

I will mention that the Ublox SARA R410 module, upon which the Nova is built, is not especially well behaved. Some of the problem I (and others on this board) regularly experience are:

1. the process for firmware updates to the Ublox module is still rocky. Some devices update without incident. Others don’t. Hologram has certainly worked hard to solve these problems, but it is not yet clear to me those problems are completely resolved.

2. the Ublox module makes it hard to determine if the connection has dropped. There are several “features” of the module which contribute to this problem.

First, if you are using the USB interface you can have only one communication line to the module. If you choose to control the device via AT commands, then you can send whatever AT commands you want, including commands to check the status of the module. If, however, you set up PPP connection, then only the ppp daemon will have access to the module so you will NOT be able to ask the module for its connection status. IMHO this is a serious design flaw. A $5 ZTE MF190 (USB 3G modem) allows two simultaneous connections to its module, so one can be handed to PPP and the other can be used to monitor connection status.

Second, Ublox has tried to make the module smart enough to handle short-term connection loss (as can happen in a mobile context after leaving the range of one cell tower (and losing the connection) until it enters the range of another cell tower). When the module loses its connection it hides this loss while waiting to establish a new connection and internally caches data during this period. However, the data cache is volatile, so if the device is powered off before it gets a new connection (and sends the cached data) the cached data is lost and the app never knows about the loss. There are possible software workarounds for this problem (which I’m happy to discuss), but you should be aware of this problem.

3. If you select a SIM/MVNO which supports connecting to more than one network provider (e.g. Verizon and ATT) the Ublox module is supposed to facilitate automatically connecting to an available provider supported by the SIM. I am not aware that anyone has gotten this functionality to work reliably.

I have posted multiple threads on this board recounting the problems I have encountered and also the results of my discussions with technical folks at Ublox. Hologram, of course, doesn’t have the necessary technical information to get to the bottom of these problems–only Ublox can really sort this out. Ublox has not been willing (or able) to sort this out.

In brief, for the the earlier firmware version, Ublox had one set of recommendations. For the new firmware they have changed their recommendations (in accordance with firmware changes to the module)–fair enough. In the new firmware, there is a new MNO profile: SIM Select. Choosing this profile is supposed to leave it to the module to consult with the SIM card and then select an appropriate, available provider and configure the module optimally for the selected provider. Ublox now says using the “old” approach is “at your own risk,” and strongly recommends using the new SIM Select profile. Fair enough, except…

…it just doesn’t work. I have identified precise sequences demonstraring the process fails, and I have demonstrated the failure in screen-shares with Ublox technical folks. They offer no solution, instead back-pedaling on the advice to use SIM Select, but only because I have demonstrated a solution which does connect using the “old” (pre-SIM Select) profile approach.

I purchased 55 Nova devices almost a year ago. I deployed them and in vehicles. The results are not good. Connectivity has not been reliable. Others also report that their Nova devices work for a while and then stop connecting.

So, the real secret sauce you’ll need probably has to come from Ublox and they are not being helpful.

My own advice is that you should think carefully about the nature of the application for which you are considering using Nova devices. If it is important that you can deploy them and expect them to work reliably for many months or years you should not be confident in choosing the Nova.

If you cannot afford to lose any data at all, and your application is mobile, the caching problem already described should be worked around before choosing the Nova.

In short, the module has exciting specs, but has not yet lived up to them.

[scobb]

Hi mbrenner,
Thanks for the feedback. It is really helpful. I noticed the shortcoming of the single serial stream just playing around testing it. In my particular application, I can live with it - as it connects once a day, dumps data then goes away. However I appreciate the other things that you bring up.

I started looking for the ZTE MF190 (USB 3G modem) that you mentioned. I haven’t found an obvious source for them - except ebay. Do you have any pointers to a reasonable souse?

Thanks for your input!

[mbrenner]

Hi @scobb,

My company buys them in pretty large quantities. What quantity are you looking for? If you like, my company can be a “reasonable source.”