[Tinyos-devel] again about the baudrate issue for telos

Chieh-Jan (Mike) Liang cliang4 at cs.jhu.edu
Tue Mar 3 00:07:39 PST 2009


Hi Andreas,

Can you elaborate more? I am interested in what code can lead to the  
high CPU load, and see if there is any work-around.

Thank you

Mike

On Mar 3, 2009, at 2:11 AM, Andreas Köpke wrote:

> Hi, this patch has one disadvantage: it makes the SF less suitable  
> for devices
> like the NSLU2: writing/reading single bytes for 8 or more telosb  
> leads to a
> high CPU load on an slug.
>
> Best, Andreas
>
> On Dienstag 03 März 2009 00:06:37 Chieh-Jan (Mike) Liang wrote:
>> Hi Eric,
>>
>> In my case, when the mote->pc packet rate is high, I get a a lot of
>> "write fail" from the C serial forwarder, even at 57600. Here are my
>> changes to the C serial forwarder:
>>
>> 1.) I have byte spacing to wait a little bit after sending each byte.
>> Currently, this is 50 micro-sec, but I think it can be lower. Byte
>> spacing was also recently added to the python T2 serial stack,  
>> tos.py.
>> The hope is that the mote has some more time to handle the interrupt.
>> 2.) Byte spacing helps a lot, but there were still some "write fail".
>> So, I retry sending a packet if such case happens. I believe the Cpp
>> serial forwarder already does this, but not the C version.
>>
>> I attached a patch. Please let me know if you see something weird.
>>
>> Thank you
>>
>> Mike




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