[Ovmsdev] Refactoring MODEM/SIMCOM for v3.3

Mark Webb-Johnson mark at webb-johnson.net
Fri Aug 21 10:41:12 HKT 2020

The prototype board I have is just a SIM7600 put onto our existing layout. In fact, the PCB layout we have was designed to work with either SIM5360 or SIM7600, interchangeably.That is the reason it has pads for three antenna sockets. The power issues are throwing a bit of a wrench into that plan.

Perhaps when I’ve finished with the firmware refactoring of modem support, your SIM7600 will work. I’m currently planning to add firmware support for the SIM7600. Not sure which final modem module we will choose - the initial firmware support is simply proof-of-concept. I like the idea of NB-IoT, and have played with SIM7020 (no GPS/GNSS though). The SIM7000 looks interesting (LTE, NB-IoT, EDGE, and GPS/GNSS).

Regards, Mark.

> On 21 Aug 2020, at 10:23 AM, Craig Leres <leres at xse.com> wrote:
> On 2020-08-20 18:26, Mark Webb-Johnson wrote:
>> Did you ever get that SIM7600 working? It certainly requires some changes to the CMUX arrangements, as there is no CMUXSRVPORT command implemented.
> Nope. I spent some time looking at the documentation and concluded it was a larger project than I wanted to engage at the time.
>> We’re also seeing high peak power usage on that module. 450ma to 600ma at 5V. Can’t run it off most laptop/computer USB 2 ports (the power draw brings voltage down to 4.5V or so, and brownouts occur). It seems to run ok on USB 3. We’re probably going to have to redesign the modem board power supply to get this working reliably. On the positive side, reception does seem better than the 5360 - I can even get a single in the cellular blackhole that is my home office.
> Interesting. The 12V wart I'm powering my dev ovms module off of is only rated for 500 mA. But I did little more than enter some AT commands and verify that it could register on the cell network.
> Better reception sounds good; my motivation in going this direction is that at a minimum it would give us a better selection of cell towers to talk to.
> 		Craig

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