CAN question
- Thread starter kam
- Start date
krypton_john
Senior Member
What, no steak knives?
There are OBDII interfaces with serial I/O. The serial can be interfaced to the PICAXE of course - you just need to fork out $$ for the interface.
This was the best I could find when looking a while back. Baud rate adjustable on this one to 128000 (unlike most which are fixed at relatively low rates);
http://tunertools.com/proddetail.asp?prod=OBDpro_serial
There is also a reasonable amount of free "dashboard display" PC software around - some supplied with this unit.
This was the best I could find when looking a while back. Baud rate adjustable on this one to 128000 (unlike most which are fixed at relatively low rates);
http://tunertools.com/proddetail.asp?prod=OBDpro_serial
There is also a reasonable amount of free "dashboard display" PC software around - some supplied with this unit.
OK post too short, Got It.
The Serial to CAN makes sense. but wouldnt it affect the Performance and cost as well?
I think i read somewhere that the CAN protocol can be achieved with some coding in C... oh i think it was an ATMEL AVR. but not too sure.
Hippy, would you consider this to be a statement long enough to be considered a POST??
look i even added some smilies
The OBDPro in the reference above is a self contained and fully tested unit. It runs on a PIC inside and as indicated can run VFast serial (or USB if you get that model).
I presume by 'performance' you mean the PICAXE program performance.
Sure it will cost and it will be slow to the extent that;
1. the car will respond to the request on the CAN bus which depends on what the car is doing - tasks are prioritised depending on what is going on - you don't really want the traction control and/or ABS braking waiting around for the hung session on your homebrew PIC code do you?!!?
2. the serial comms speed.
I don't know what your application is but I for one certainly would not mess with a homebrew CAN interface unless on a completely non critical system (which I could not conceive of having a CAN in the first place).
Depending on what you want to read (or heaven forbid - control) you could obtain the information by other means.
e.g if it is engine speed or road speed, you could try ignition pickups or hall effect sensors on rotating parts - these are also available with ratiometric outputs so they can be read directly by READADC.
But it's your application so its OTY!
I presume by 'performance' you mean the PICAXE program performance.
Sure it will cost and it will be slow to the extent that;
1. the car will respond to the request on the CAN bus which depends on what the car is doing - tasks are prioritised depending on what is going on - you don't really want the traction control and/or ABS braking waiting around for the hung session on your homebrew PIC code do you?!!?
2. the serial comms speed.
I don't know what your application is but I for one certainly would not mess with a homebrew CAN interface unless on a completely non critical system (which I could not conceive of having a CAN in the first place).
Depending on what you want to read (or heaven forbid - control) you could obtain the information by other means.
e.g if it is engine speed or road speed, you could try ignition pickups or hall effect sensors on rotating parts - these are also available with ratiometric outputs so they can be read directly by READADC.
But it's your application so its OTY!
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Some micros have CAN Bus interfaces on-chip, others can handle one by bit-banging. Otherwise an external ( eg, CAN to serial, CAN to I2C ) interface will be required. That will likely have an effect on throughput, but then so would the speed of operation of a PICAXE.
Whether performance is affected depends on what is being sent, received or monitored; as long as the PC/processor can handle the dtaa before the next must be there may be some latency issues but no overall loss of performance.
Whether performance is affected depends on what is being sent, received or monitored; as long as the PC/processor can handle the dtaa before the next must be there may be some latency issues but no overall loss of performance.
If Microchip ever produce a PICmicro with CAN interface which gets used as a PICAXE we might see some means to use it, although it's a bit specialised for the main PICAXE target market.
We'll just have to have a pro-forma template made up for responding to, "3l33t h4xor wants BOOST Firebird-T to 480bhp hlp dad sez ok pls will pay $$$".
We'll just have to have a pro-forma template made up for responding to, "3l33t h4xor wants BOOST Firebird-T to 480bhp hlp dad sez ok pls will pay $$$".
BeanieBots
Moderator
My thoughts tooWe'll just have to have a pro-forma template made up for responding to, "3l33t h4xor wants BOOST Firebird-T to 480bhp hlp dad sez ok pls will pay $$$".