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ELM320 参数 Datasheet PDF下载

ELM320图片预览
型号: ELM320
PDF下载: 下载PDF文件 查看货源
内容描述: OBD ( PWM) ,以RS232翻译 [OBD (PWM) TO RS232 INTERPRETER]
分类和应用:
文件页数/大小: 16 页 / 100 K
品牌: ELM [ ELM ELECTRONICS ]
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ELM320  
AT Commands (continued)  
I
[ Identify yourself ]  
the MA and MR monitoring modes, any RS232  
activity (single character) aborts the monitoring.  
Issuing this command causes the chip to identify  
itself, by printing the startup product ID string (this is  
currently ‘ELM320 v2.0’). Software can use this to  
determine exactly which integrated circuit it is talking  
to, without resorting to resetting the entire IC.  
PD  
[ send Packed Data ]  
This option is for those that are building a computer  
interface and want the fastest data transfer rate  
possible while still operating at 9600 baud. When  
selected, responses from the vehicle will be  
formatted as an initial length byte followed by the  
actual response bytes from the vehicle, with no  
trailing carriage returns or linefeed characters. The  
data will not be altered in any way, except for the  
conversion to standard RS232 bytes.  
L0 and L1  
[ Linefeeds off (0) or on(1) ]  
Whether the ELM320 transmits a linefeed character  
after each carriage return character is controlled by  
this option. If an ATL1 is issued, linefeed generation  
will be turned on, and for ATL0, it will be off. Users  
may wish to have this option on if using a terminal  
program, but off if using a custom interface (as the  
extra characters transmitted will only serve to slow  
the vehicle polling down). The default setting is L1  
(linefeeds on)  
Note that the length byte only represents the total  
number of data bytes following, and does not include  
itself. Also, if there was a data (checksum) error, the  
length byte will have its most significant bit set, so  
the user should always check first to see if the length  
is greater than 127. (The other 7 bits still provide a  
valid byte count if there is an error, so one need only  
ignore the msb, or subtract 128 from the value.)  
MA  
[ Monitor All messages ]  
Using this command places the ELM320 into a bus  
monitoring mode, in which it displays all messages  
as it sees them on the OBD bus. This continues  
indefinitely until stopped by activity on the RS232  
input. To stop the monitoring, one should send any  
single character then wait for the ELM320 to respond  
with a prompt character (‘>’). Waiting for the prompt  
is necessary as the response time is unpredictable,  
varying depending on the IC was doing when  
interrupted. If for instance it is in the middle of  
printing a line, it will first complete the line then  
return to the command state, issuing the prompt  
character. If it were simply waiting for input, it would  
return immediately. The character which stops the  
monitoring will always be discarded, and will not  
affect subsequent commands.  
A ‘NO DATA’ response has no data bytes, but still  
sends a length byte with value ‘0’.  
R0 and R1  
[ Responses off (0) or on(1) ]  
These commands control the ELM320’s automatic  
display of responses. If responses have been turned  
off, the IC will not wait for anything to be returned  
from the vehicle after sending a request, and will  
return immediately to waiting for RS232 commands.  
This is useful if sending commands blindly when  
using the IC for a non-OBD network application, or  
simulating an ECU, in a basic learning environment.  
It is not recommended that this option normally be  
used, however, as the vehicle may have difficulty if it  
is expecting an acknowledgement byte and never  
receives one. The default is R1 (responses on).  
MR hh  
[ Monitor for Receiver hh ]  
This command also places the IC in a bus monitoring  
mode, displaying only messages that were sent to  
the hex address given by hh (i.e. messages which  
are found to have that value in their second byte).  
Any RS232 activity (single character) aborts the  
monitoring, as with the MA command.  
SH xx yy zz  
[ Set the Header to xx yy zz ]  
This command allows the user to control the values  
that are sent as the three header bytes in the  
message. The value of hex digits xx will be used for  
the first or priority/type byte, yy will be used for the  
second or target byte, and zz will be used for the  
third or source byte. These remain in effect until set  
again, or until restored to the default values with the  
AT D, or AT Z commands. The default header values  
MT hh  
[ Monitor for Transmitter hh ]  
Another monitoring command, which displays only  
messages sent by Transmitter address hh. As with  
ELM320DSC  
Elm Electronics – Circuits for the Hobbyist  
< http://www.elmelectronics.com/ >  
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