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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  
Restoring Order  
There may be times when it seems the ELM329 is  
may be necessary to do something more drastic - like  
resetting the entire IC. There are a few ways that this  
can be performed with the ELM329. One way is to  
simply remove the power and then reapply it. Another  
way that acts exactly the same way as a power off and  
then on is to send the full reset command:  
out of control, and you will need to know how to  
restore order. Before we continue to discuss modifying  
too many parameters, this seems to be a good point to  
discuss how to ‘get back to the start’. Perhaps you  
have told the ELM329 to monitor all data, and there  
are screens and screens of data flying by. Perhaps the  
IC is now responding with ‘NO DATA’ when it did work  
previously. This is when a few tips may help.  
The ELM329 can always be interrupted from a  
task by a single keystroke from the keyboard. As part  
of its normal operation, checks are made for received  
characters and if found, the IC will stop what it is doing  
at the next opportunity. Often this means that it will  
continue to send the information for the current line,  
then stop, print a prompt character, and wait for your  
input. The stopping may not always seem immediate if  
the RS232 send buffer is almost full, though – you will  
not actually see the prompt character until the buffer  
has emptied, and your terminal program has finished  
printing what it has received.  
There are times when the problems seem more  
serious and you don’t remember just what you did to  
make them so bad. Perhaps you have ‘adjusted’ some  
of the timers, then experimented with the CAN filter, or  
perhaps tried to see what happens if the header bytes  
are changed. If you have been experimenting with  
CAN filters and are suddenly seeing ‘NO DATA’  
responses, this can usually be fixed by resetting the  
filters. Simply send:  
>AT Z  
It takes approximately one second for the IC to  
perform this reset, initialize everything and then test  
the four status LEDs in sequence. A much quicker  
option is available with the ELM329, however, if the  
led test is not required – the ‘Warm Start’ command:  
>AT WS  
The AT WS command performs a software reset,  
restoring exactly the same items as the AT Z does, but  
it omits the LED test, making it considerably faster.  
Also, it does not affect any baud rates that have been  
set with the AT BRD command (which AT Z does), so  
is essential if you are modifying the RS232 baud rates  
with software.  
Any of the above methods should be effective in  
restoring order while experimenting. There is always  
the chance that you may have changed  
a
Programmable Parameter, however, and are still  
having problems with your system. In this case, you  
may want to simply turn off all of the Programmable  
Parameters (which forces them to their default values).  
To do so, send the command:  
>AT CRA  
OK  
>AT PP FF OFF  
and the filter and mask will be reset to the default  
values.  
If you problem is more involved than this, then all  
of the settings can be reset by sending the ‘set to  
Defaults’ command:  
which should disable all of the changes that you have  
made. Since some of the Programmable Parameters  
are only read during a system reset, you may have to  
follow this command with a system reset:  
>AT Z  
>AT D  
OK  
after which, you can start over with what is essentially  
a device with ‘factory settings’. There may be times  
when even this command is not recognized, however.  
If that is the case, you will need to use the hardware  
method of turning the PPs off. See the section on  
‘Programmable Parameters’ (pages 59 and 60) for  
more details.  
This will often be sufficient to restore order, but it  
can occasionally bring unexpected results. One such  
surprise will occur if you are connected to a vehicle  
using one protocol, but the saved (default) protocol is  
a different one. In this case, the ELM329 will close the  
current session and then change the protocol to the  
default one, exactly as instructed.  
If the AT D does not bring the expected results, it  
ELM329DSB  
Elm Electronics – Circuits for the Hobbyist  
www.elmelectronics.com  
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