[Ovmsdev] Without SMS
mark at webb-johnson.net
Wed Sep 19 09:14:26 HKT 2012
Trying to work out ways to provision OVMS modules without SMS.
One way is the new DIAG port SETUP mode. But, that requires a RS232 connection to the PC (not so easy nowadays, with a USB-RS232 adaptor required for most laptops). Also kind of messy for v1 modules.
Another way is phonebook entries on the SIM card. The problem here is that you need some way to create the phone book entries. With older 'feature' phones, that was easy. But, now in the days of iPhone I suspect more tricky. Another problem is that the number field can only be numbers, not alpha-numeric, so textual data must go in the phonebook entry name field itself.
For the SIM card phonebook, I'm thinking of two approaches:
Create phonebook entries like "O-8-MYVEHICLEID", "O-5-APN", etc. The O- prefix tells us this is OVMS, the next number is the parameter number to set, and the remainder is the value. This is very flexible, but the textual fields are limited in length (typically 16 characters or so), and it looks kind of messy.
For specific providers, we could do an auto-provisioning. Something like create a phonebook entry on the SIM 'OVMS-AUTO' with number 0. The number references an auto-provisioning profile, and that just provides the cellular network APN, user and password. The system would then use those to establish a GPRS connection, learn the SIM ID from the SIM, learn the vehicle VIN from the can bus, then provide both to the OVMS server. A shared secret is required here, and we have two private pieces of information, so this should be ok. We can encrypt with the SIM ID, and provide the VIN as the key. The OVMS server would lookup the VIN key provided, decrypt and check it against the SIM ID, and if all is ok could provide back a similarly encrypted provisioning profile containing everything else required (all the other parameters). For this to work, the SIM would just have to have that special "OVMS-AUTO" phonebook entry created.
The main reason I'm thinking about this is for the globalsimcard provider I'm working with. They can provide SIM cards that work globally for data only, with pretty good rates. Cards are good for 12 month validating and can be renewed for another year for less than US$10. Monthly cost should be US$1 + data, hassle free, and data should be less than US$2 for most providers. If we can auto-provision these, then setup should be to configure the provisioning information as you want, on the server, then just plug the SIM in and go.
Every SIM card issued has a defined prefix in its ID. I'm trying to find out of the globalsimcard prefix will always be the same, and will always differentiate these from others. If so, then we can auto-provision based on SIM ID as well (without even needing the OVMS-AUTO phonebook entry).
What do people think? How easy would it be for people nowadays to create a phonebook entry on a SIM card?
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