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ELM329P 参数 Datasheet PDF下载

ELM329P图片预览
型号: ELM329P
PDF下载: 下载PDF文件 查看货源
内容描述: CAN解释 [CAN Interpreter]
分类和应用:
文件页数/大小: 76 页 / 353 K
品牌: ELM [ ELM ELECTRONICS ]
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ELM329  
Overview  
The following describes how to use the ELM329 to  
this product as well.  
obtain information from your vehicle.  
Using the ELM329 is not as daunting as it first  
seems. Many users will never need to issue an ‘AT’  
command, adjust timeouts, or change the headers. For  
most, all that is required is a PC or smart device with a  
terminal program (such as HyperTerminal or ZTerm),  
and a little knowledge of OBD commands, which we  
will provide in the following sections…  
We begin by discussing just how to ‘talk’ to the IC  
using a PC, then explain how to change options using  
‘AT’ commands, and finally we show how to use the  
ELM329 to obtain trouble codes (and reset them). For  
the more advanced experimenters, there are also  
sections on how to use some of the other features of  
Communicating with the ELM329  
The ELM329 expects to communicate with a PC  
through an RS232 serial connection. Although modern  
computers do not usually provide a serial connection  
such as this, there are several ways in which a ‘virtual  
serial port’ can be created. The most common devices  
are USB to RS232 adapters, but there are several  
others such as PC cards, ethernet devices, or  
Bluetooth to serial adapters.  
No matter how you physically connect to the  
ELM329, you will need a way to send and receive  
data. The simplest method is to use one of the many  
‘terminal’ programs that are available (HyperTerminal,  
ZTerm, etc.), to allow typing the characters directly  
from your keyboard.  
To use a terminal program, you will need to adjust  
several settings. First, ensure that your software is set  
to use the proper ‘COM’ port, and that you have  
chosen the proper data rate - this will be either 9600  
baud (if pin 6 = 0V at power up), or 38400 baud (if  
pin 6 = 5V and PP 0C has not been changed). If you  
select the wrong ‘COM’ port, you will not be able to  
send or receive any data. If you select the wrong data  
rate, the information that you send and receive will be  
all garbled, and unreadable by you or the ELM329.  
Don’t forget to also set your connection for 8 data bits,  
no parity bits, and 1 stop bit, and to set it for the proper  
‘line end’ mode. All of the responses from the ELM329  
are terminated with a single carriage return character  
and, optionally, a linefeed character (depending on  
your settings).  
computer connections and terminal software settings  
are correct (however, at this point no communications  
have taken place with the vehicle, so the state of that  
connection is still unknown).  
The ‘>’ character that is shown on the second line  
is the ELM329’s prompt character. It indicates that the  
device is in the idle state, ready to receive characters  
on the RS232 port. If you did not see the identification  
string, you might try resetting the IC again with the AT  
Z (reset) command. Simply type the letters A T and Z  
(spaces are optional), then press the return key:  
>AT Z  
That should cause the LEDs to flash again, and  
the identification string to be printed. If you see strange  
looking characters, then check your baud rate - you  
have likely set it incorrectly.  
Characters sent from the computer can either be  
intended for the ELM329’s internal use, or for  
reformatting and passing on to the vehicle. The  
ELM329 can quickly determine where the received  
characters are to be directed by monitoring the  
contents of the message. Commands that are  
intended for the ELM329’s internal use will begin with  
the characters ‘AT’, while OBD commands for the  
vehicle are only allowed to contain the ASCII codes for  
hexadecimal digits (0 to 9 and A to F).  
Whether it is an ‘AT’ type internal command or a  
hex string for the OBD bus, all messages to the  
ELM329 must be terminated with a carriage return  
character (hex ‘0D’) before it will be acted upon. The  
one exception is when an incomplete string is sent and  
no carriage return appears. In this case, an internal  
timer will automatically abort the incomplete message  
after about 20 seconds, and the ELM329 will print a  
single question mark (‘?’) to show that the input was  
not understood (and was not acted upon).  
Properly connected and powered, the ELM329 will  
energize the five LED outputs in sequence (as a lamp  
test) and will then send the message:  
ELM329 v2.0  
>
In addition to identifying the version of this IC,  
receiving this string is a good way to confirm that the  
Messages that are not understood by the ELM329  
ELM329DSB  
Elm Electronics – Circuits for the Hobbyist  
www.elmelectronics.com  
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