After hours of reading and trial and error I can tell for sure that the data is there ... now I'm trying to read it using an arduino mega.But having some issues since they have a different pattern for the serial - then one that I could find on the begin command.I know its baud 96 (100) ...I made several attempts of reading the data (via Seral1 - baud 100 in all the 2 end bit options) and sending it to the computer via the Serial.I get an output but can not make a pattern out of it - and I'm guessing it has to do with the starting 16bit + 4bit as shown in the PDF.Any one can help me out with a code that might help me over come this issue ?
Toyota Obd1 Serial Interface For Arduino
A microcontroller based automotive computer interface is described. The device utilizes a propriety serial interface to connect to an automotive engine control computer and retrieve current engine conditions. This information is then processed and output to a LCD. The hardware, software, and interface details are described.
The GM 8192 baud OBD-I ALDL interface was the second and last of the two OBD-I interfaces. The 8192 baud interface communicates over pin M of the ALDL connector. The 8192 baud interface is more complex, faster, allows for more control of diagnostic data, and more diagnostic data to be retrieved from the ECU. The 8192 baud interface only uses one wire like the 160 baud interface but uses an asynchronous serial communication method and allows for two way communications over a single data line. The 8192 baud interface protocol is also a master/slave protocol and allows for multiple devices internal and external to the automobile to be connected to it. The ECUs that implement a 8192 baud interface do not constantly output data like the 160 baud interface; instead the attached device must send a short message requesting data from the ECU and the ECU will respond with a 60+ byte burst of data depending on the model of automobile, ECU, and code mask running on the ECU.
The 8192 baud ALDL interface uses an asynchronous serial communication method as a means to transfer data over the data line. The 8192 baud interface also has a predetermined software communication procedure which can be considered the 8192 baud protocol. The 8192 baud interface uses asynchronous serial communication to perform the physical task of transmitting and receiving data. Asynchronous serial communication uses a start signal prior to each byte and a stop signal after each byte of data sent. This is the same method a serial RS-232 port on a computer uses with the difference that a RS-232 port has a separate transmit and receive line. In asynchronous serial communication the number of bits to be transmitted between start and stop bits, number of stop bits, parity options, and baud rate must be defined prior to any communication. The 8192 baud ALDL interface uses eight bits with one stop bit and no parity as seen in the timing diagram of Figure 6 below. The 8192 baud protocol uses an off standard baud rate of 8192 samples per second as the name implies. The closest standardized baud rate is 9600, this requires more effort in the hardware and software design to accommodate this off standard baud rate which is discussed later in this document.
An Atmel Mega324P AVR microcontroller was selected in this project to communicate and process the ECU data. This data is then output to a Hitachi 44780 controller based 420 LCD. The details of the AVR microcontroller and why it was chosen over similar microcontrollers, like a Microchip PIC microcontroller, is discussed below because is it outside the scope of this section. The Mega324P AVR is the most powerful AVR in a 40 pin DIP package, in production at the time of this report.The Universal Asynchronous Receiver/Transmitter (UART) built into the Mega324P is designed to work with serial communication methods that use separate transmit and receive data lines such as SCI and SPI. The Mega324P, as with most microprocessors, is not designed to work with the off standard one wire interface used in this project. An interface circuit is needed to convert the one ALDL serial line to two data lines: a transmit line and a receive line. 2ff7e9595c
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