garygid wrote:Good thinking, it should make a good DIY project, but beyond most people's skills.
1. I think I also have a $13 JTAG programmer from ebay, if it actually works. If not, I believe there is another "tiny", low-cost, USB-to-JTAG programmer from SparkFun that will work. I have it on order.
2. Do you need to add the CAN transeiver as on the AVR-CAN board?
3. Do you need an RS232 level-generator & transeiver chip, with some caps?
4. The display needs to be mounted and its 4 + 8 = 12 lines connected to the uP board.
5. DB9F connector for the RS232 connection?
6. DB9M (or on-board holes) for connecting the four OBD cable wires?
7. Additional power regulator to handle the 14v from the car?
8. Will you make a daughter board to hold/do this stuff?
9. The labor to program, build, test, and assemble is fine for a skilled person's DIY Project, but might end up saving very little (or actually cost more) when producing a number of units, but still in low quantity.
However, if you are serious about the project, we will watch and comment, if you wish.
Moderator, please take my post and the previous one and start a "DIY AT90CAN CAN-Capture Project" thread. Thanks.
You have many valid questions.
I didn't know there were such cheap JTAG programmers on eBay. That's great if you can get one to work. One thing USBtinyISP is that it works easily with the Arduino IDE.
I didn't realize that a separate transceiver chip was needed, but adding a MCP2551 isn't all too hard.
Yes, I'm aware of the requirements for hooking up a display. At this moment, though, I'm more interested in USB connectivity to a Windows PC
I'm not going to do any RS-232 conversion. None of my PC's have an RS-232 port. It's easier to go straight from the uC to a USB->Serial converter.
Yes, 14V needs to be dealt with. Some additional components can handle that. To start, I was going to just hack a 9V cigarette lighter adapter that I have laying around.
One of the things I didn't like about the other board is the DB9 connectors. I'm buying an OBD cable with stripped ends, so it's easier for me to just attach them directly to the headers.
I'm just going to breadboard the thing while debugging it. Then I'll decide how I'll assemble something more compact to put in the car. Initially, I'll probably just
put all the parts on a proto board.
For volume production, a custom PCB would save a lot on cost. Right now, I'm just interested in hacking something together so I can play.