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ELM327_13 参数 Datasheet PDF下载

ELM327_13图片预览
型号: ELM327_13
PDF下载: 下载PDF文件 查看货源
内容描述: OBD转RS232解释 [OBD to RS232 Interpreter]
分类和应用:
文件页数/大小: 82 页 / 393 K
品牌: ELM [ ELM ELECTRONICS ]
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ELM327  
Communicating with the ELM327 (continued)  
question mark. These include incomplete messages,  
incorrect AT commands, or invalid hexadecimal digit  
strings, but are not an indication of whether or not the  
message was understood by the vehicle. One must  
keep in mind that the ELM327 is a protocol interpreter  
that makes no attempt to assess the OBD messages  
for validity – it only ensures that hexadecimal digits  
were received, combined into bytes, then sent out the  
OBD port, and it does not know if a message sent to  
the vehicle was in error.  
While processing OBD commands, the ELM327  
will continually monitor for either an active RTS input,  
or an RS232 character received. Either one will  
interrupt the IC, quickly returning control to the user,  
while possibly aborting any initiation, etc. that was in  
progress. After generating a signal to interrupt the  
ELM327, software should always wait for either the  
prompt character (‘>’ or hex 3E), or a low level on the  
Busy output before beginning to send the next  
command.  
commands may be entered as you prefer, as no one  
method is faster or better. The ELM327 also ignores  
space characters and all control characters (tab, etc.),  
so they can be inserted anywhere in the input if that  
improves readability.  
One other feature of the ELM327 is the ability to  
repeat any command (AT or OBD) when only a single  
carriage return character is received. If you have sent  
a command (for example, 01 0C to obtain the rpm),  
you do not have to resend the entire command in  
order to resend it to the vehicle - simply send a  
carriage return character, and the ELM327 will repeat  
the command for you. The memory buffer only  
remembers the one command - there is no provision in  
the current ELM327 to provide storage for any more.  
Finally, it should be noted that the ELM327 is not  
case-sensitive, so the commands ‘ATZ’, ‘atz’, and  
‘AtZ’ are all exactly the same to the ELM327. All  
Please Note:  
There is a very small chance that NULL characters (byte value 00) may occasionally  
be inserted into the RS232 data that is transmitted by the ELM327.  
Microchip Technology has reported that some ICs which use the same EUSART as  
in the ELM327 may, under very specific (and rare) conditions, insert an extra byte  
(always of value 00) into the transmitted data. If you are using a terminal program to view  
the data, you should select the ‘hide control characters’ option if it is available, and if you  
are writing software for the ELM327, then ignore incoming bytes that are of value 00 (ie.  
remove NULLs).  
ELM327DSI  
Elm Electronics – Circuits for the Hobbyist  
8 of 82  
www.elmelectronics.com