We have prototypes for both 4G and NB-IoT/Cat-M1 modules. While it is simple to make these (bearing in mind the firmware support requirements), the primary issue is certification. Each modem+module combination needs to be certified (CE+ROHS for EU, FCC for US), and that is a substantial upfront cost. The more modem combinations we have, the higher the cost. We simply cannot justify, given the volumes we have, offering EU and US variants of NB-IoT, CAT-M1, and 4G modem modules. That would be six certification fees, upfront.

Regarding NB-IoT/Cat-M1, while they are theoretically lower power, we haven't seen much difference on our bench testing of these actual modules. But the primary issue is network availability. The Hologram article below outlines the issue quite well. Certainly, in future, NB-IoT/Cat-M1 will be widespread, at the moment it is not globally available (even today, one year after the article was written). Today, we cannot use either NB-IoT or Cat-M1 everywhere that OVMS is currently used.

Our current approach is focused on a new 4G modem module, compatible with our exisitng OVMS v3.2 main board (so everyone can upgrade); certified and released along with a new v3.3 main board addressing some hardware optimisation and improvements. We hope to have this available this year - but a lot depends on the certification work and firmware suppot (which is proving harder than we anticipated).

https://www.hologram.io/blog/nb-iot-vs-cat-m1-vs-cat-1

Still very much open to feedback on this, but my current focus is on the SIM7600 module, as that gives us good backwards compatibility, a simple upgrade path, and can be used globally (with our usual two variants).

Regards, Mark.

On 25 Jul 2021, at 1:49 AM, Michael Balzer <dexter@expeedo.de> wrote:

Signed PGP part
Mark, Derek,

quoting from markus-k https://www.openvehicles.com/comment/7683#comment-7683

Can I ask what speaks against going to a NB-IoT/LTE Cat-M module? Should be ideal for this application since it doesn't require high bandwidths and has very low power consumption.

I think he has a point there.

LTE Cat M would provide more than enough bandwidth for our use, even NB-IoT would be sufficient. From what I've read Cat M is better suited for mobile application due to cell handover support.

Not sure if we would actually save power there, but it also seems these protocols are better suited for sleep modes.

Maybe the SIM7000E is worth a closer look. Or maybe changing to another manufacturer for this, e.g. the u-blox SARA-R422M8S seems to fit feature wise, also includes multiplexer support on the UART.

Regards,
Michael


Am 04.07.21 um 11:19 schrieb Mark Webb-Johnson:
Derek,

I have a SIM7000E on my desk, but haven’t played around with it much. I think the SIM7600 is more suitable for what we need (and closest to the SIM5360 it replaces).

I don’t think the CMUXPORT commands work on that module, and not sure if it even has a CMUX. The manual does mention it in one place, but not sure. It mentions compatibility with the SIM800, which does have CMUX.

What version of firmware are you running on the SIM7000?

Regards, Mark.

On 4 Jul 2021, at 3:46 PM, Derek Caudwell <d.caudwell@gmail.com> wrote:

Hi all,

I've been using Realterm to look at the 7000G's capabilities, and although the documentation only makes indirect reference to supporting uart multiplex mode, it does accept the AT+CMUX=0 command and reports back configuration values when queried with AT+CMUX? Unfortunately that appears to be where its support ends, the device responds with OK to the CMUX command however there is no response to the SABM command to open the control channel. I am sending the following hex in Realterm $F9 $03 $3F $01 $1C $F9.

Is there anything else worth trying? or that I'm missing in setting up the CMUX?

Cheers
Derek
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