Hi all, I'd like to resurrect an old conversation. As we know, the current PIC is quickly running out of resources and maybe it's time to switch to a better platform. Two CAN buses are now desirable too. A microSD slot and direct USB connectivity wouldn't hurt either. I will probably have to design a similar hardware for myself, so I'd like to contribute to the OVMS by sharing the HW platform if you want; no strings attached of course, if you decide that there's no need for the upgrade, I'll keep on working on my project by myself! :) That said, I'd like to throw a few ideas to the table.
- MCU: I'd like to use an STM32 micro. They seem to be emerging as the standard choice for diy ARM projects, and this offers a few interesting opportunities: -Programming it in c/c++ with the manufacturer CMSIS standard libraries (boring) -Programming it with the mbed.org SDK. Unfortunately no dev boards are available with dual CAN bus, but it will be easy to move to the correct micro of the same series once most of the software is ironed out on a dev board like the https://mbed.org/platforms/ST-Nucleo-F302R8/ -Programming it with an RTOS. NuttX would be my choice, as it's the one used in the Ardupilot Pixhawk platform, and I'd like to learn it. This would mean a steeper starting curve, but a lot of flexibility later as a lot of stuff is handled on the OS level (network stacks, SD card & filesystems, multitasking...). FreeRTOS is a nice option too.
I'd like to use the STM32F405RG as it's the most similar to the one found on the Pixhawk, but of course I'm biased because of that, and that micro is quite overkill for the task. We can of course use a lower specced part and lose some RTOS fuctionality as long as it has 2 CAN buses.
MODEM: I have no experience in this field; is the SIM908 still a good choice or does anyone think that we should try new platforms? I like this, but I don't know if the price puts it out of budget: http://www.telit.com/telit/Pulsar/en_US.Store.display.1001./ge864-gps On the bright side, it can be programmed in python, so we can offload some of the work to the modem. This *could* allow us to free some space on the PIC, and keep that platform without changing MCU..
Enclosure: I think that, even with the new MCU, we can still fit the old enclosure. Is that ok, or should we think about a more automotive-friendly one? Maybe waterproof for the twizy?
And that's it. I think that the core SW developers should voice their opinion, as there is a lot of work to be done on that front. A huge problem will be keeping backwards compatibility to add features for the v2 users, so we should discuss about this too.
Regards MG