DSP5 CAN Messages.

[GMPX]

Yeah for new hardware a discrete VPW bus<> CPU interface and software VPW emulation in the CPU, a lot harder for sure but it means we never get caught with supply issues.
From what I know of the ELM it is pretty cool for a lot of comms stuff, but I don't think it would have the 'grunt' to be used for CAN programming applications where blocks of 2048 bytes are sent up at once.

[Chavez91]

Sounds like a solid plan.

Yeah, for my small projects the ELM has done alright. Just looking for more things to tinker with as I get bored.
The DSP switching seemed like something fun to learn. Just wasn't sure if it was some top secret thing or not.

[DURAtotheMAX]

Josh, you can use an ELM327, couple fast-acting NPN and PNP transistors, some schottky diodes and a few resistors to easily interface an ELM327, STN1100, or ELM322 to J1850 VPW. It works fine for doing things like cluster/DIC messages, controlling things like door locks and other modules, and DSP-switching on 01-05.

[DURAtotheMAX]

Yeah for new hardware a discrete VPW bus<> CPU interface and software VPW emulation in the CPU, a lot harder for sure but it means we never get caught with supply issues.
From what I know of the ELM it is pretty cool for a lot of comms stuff, but I don't think it would have the 'grunt' to be used for CAN programming applications where blocks of 2048 bytes are sent up at once.

bit-banging VPW, I bet that was fun to code LOL!!

Yeah the ELM322/ELM327/STN1100 probably wouldnt be suited to reprogramming or high speed logging, because it only supports standard 10.4k regular communications mode, it doesnt support 41.6k VPW high speed mode I dont think.

[DURAtotheMAX]

We don't use ELM chips in our hardware, the Infineon CPU we are currently using in V2/AC has a VPW processing module built in (which is one of the main reasons we picked it), the hard chips to get are the 8 pin IC's that connect the VPW bus to the CPU (I don't recall the actual Freescale part number of it).

Phillips/NXP AU5780A is what you're referring to. I think they might be available on Alibaba as chinese knockoffs/leftovers, but I havent been able to find a legit source for "real" ones yet.

The good news is you can effectively do the same thing as the AU5780A chip with resistors, transistors, diodes, and a +8v linear regulator. Its just annoying because it makes your circuit much bigger and more complicated. And then you have to add your own external EMC/transient protection as well.

Its really obnoxious that VPW transceivers have completely disappeared. I know its not used anymore in new automotive applications, but forcing end-of-lifecycle on a chip as widely used as the AU5780A after only 5 years or so is ridiculous IMO.

[DURAtotheMAX]

Josh- Heres a schematic I drew up for a simple VPW interface circuit. It works fine. Its similar to the circuit that ELM suggests, but I had to add a couple extra components to make it more reliable.

Some of the resistor values might have to be changed slightly to work with 5v versus 3.3v. But try it as-is first. At your own risk of course.

[Chavez91]

Yeah the ELM322/ELM327/STN1100 probably wouldnt be suited to reprogramming or high speed logging, because it only supports standard 10.4k regular communications mode, it doesnt support 41.6k VPW high speed mode I dont think.

Yeah, the ELM doesn't support VPW4x. Just 10.4k as you said.

[Chavez91]

Josh- Heres a schematic I drew up for a simple VPW interface circuit. It works fine. Its similar to the circuit that ELM suggests, but I had to add a couple extra components to make it more reliable.

Some of the resistor values might have to be changed slightly to work with 5v versus 3.3v. But try it as-is first. At your own risk of course.

Thanks, Ill try that one out also with the STN1110. 3.3v would be nicer as well instead of the 5v.

[Chavez91]

Looks like the ELM only supports 8bytes for transmitting. Doesn't support block mode transmits or 4x. Not sure if that could pose a problem. Not sure if the STN1110 or 1170 do either? I read that they have the 4x capability but wasn't implemented in the firmware? Do you know that answer Ben?

[DURAtotheMAX]

All databus messages, whether its CAN or J1850VPW, they're all 8-byte max.

Well, 8 bytes plus header. For J1850 the header is 3-bytes long. Priority, target node, source node.

The ELM327/322, and STN1110 chips will do everything you want to do as far as DSP switching. The only thing they wont do is high speed 4x logging and reflashing.