A complete newbie, what I am trying to do put together a PCB that translates the vehicles speed and outputs this in an analogue speed format, that is to say 1 Hz per every 1 mph.
I intend to use the STN1110 as the front end and use a Atmega IC to communicate with the STN110 on board, the reason I have decided on the STN1110 is simply that is multi protocol, and low cost compared to the ELM series, and also can be updated.
I have searched on this forum and the net for PCB designs that I can use for the front end, nearly all designs that I come across are for connection to a pc via a DB9.
But I have come across the this PCB that uses the STN1110 SparkFun OBD-II UART - WIG-09555 - SparkFun Electronics which is designed for DB9 connection, which I guess could be reworked to include an Atmega IC, but I am not sure how to do this
So my questions are as follows:
(1) Is there a Atmega IC that has a ADC output pin.
(2) Is there an existing PCB design based around a STN1110 which uses an Atmega Ic
Any pointers or advice would be much appreciated, thx in advance
Thx for the reply cyclegadge and for the links. Yes you can say it’s a single purpose tool, a standalone tool. It is not for diagnostic use
Quite simply on the intended PCB the front end is the can bus interpreter, the intended Atmega IC is the intend controller, I intend to write the code for (that sends requests to the interpreter the STN1110,) the only output from this standalone PCB will be an analogue speed signal, via a single wire.
The OBD shield you linked can only communicate in a few protocols, the reason I selected the STN1110 PCB because it communicates in all protocols, in truth it’s the STN1110 firmware that does all the work the Atmega simply sends requests in the ELM format and receives the reply in ELM format(no matter what vehicle it is connected to), the reply is translated into some form of ADC signal which can be outputted by a single wire.
What i should be asking is I suppose is how do I "drop" in the intended Atmega 328 into the PCB design and add a ADC output
The datasheet shows that the STN1110 has TTL serial on pins 16 and 17. Simply connect the arduino to those and then write the relevant code to send a command and the recieve the data. You'd then interpret the data and use it to produce the output signal.
The output you require - is it a sine wave? square wave? what is the range? if it's 0 - 5v then the arduino can probably do it (maybe with a low pass filter). If it's greater than this - a transistor would be required. As it's to be used in an automotive environment it might be wise to use an optoisolater.
What was so apparent to you was not to me and thanks for that, regarding wave? square wave? this does not make a difference it can be either, the range 0 to 12V.
Regarding the optoisolater I presume this should be inline on the output, to protect the PCB, and indirectly i guess the car also
As it seems this project is feasible, I guess i can order parts and start bread boarding first.
If its of any use to anybody else Microchip have a mufti protocol IC that is comparable to the STN1110 in beta.
Any other pointer or suggestions greatly accepted.