SMAC data loss

saurabh — Wed, 30 Jul 2008 18:27:18 GMT

I am using SMAC. The code is generated using Beekit, the accelerometer project in the SMAC section. The ADC in that example is 8-bit and the 3 bytes of data that is transferred from the Accelerometer SRB to the SRB that is connected the PC.

Only thing I have changed is the ADC is now 10bits so 6 bytes are transferred from the Accelerometer SRB to the SRB that is connected the PC.

When I collect the data on the PC using a hyperterminal program I can see that there is some loss of data. To investigate it further I changed the sending code on the Accelerometer. Instead of reading the accl values and sending them to the other SRB I worte a function that has three 16bit unsigned variables first with value 0, second with value 100 and third with value 200. I have put all these variables in the transmit buffer. The transmit buffer being 8bit unsigned, I had to split the the variable, with MSB put in the buffer first followed by the LSB.

I have captured the bytes on the PC using a hyperterminal program for atleast 90seconds. By analyzing the received data I can see that I don't get the values in series.i.e I get value 0 100 200. then I get 2 102 202. This shows that I encounter packet loss.

I tried this on the 8-bit code as ws generated using Beekit. I just modified the sending part as above but only for 8-bit values. This also gave me the same results. I do see data loss.

Has any one observed data loss in using SMAC for communication. My application being critical I can't afford data loss. Does MAC(802.15.4) have data loss too.

Re: SMAC data loss

Mads — Tue, 05 Aug 2008 23:05:57 GMT

saurabh,

The SMAC supplies you with primitives to send and receive data, but it does not like 802.15.4 have an acknowlegdement scheme build in.

This is up to you to implement if it is required by your application.

As you are using a wireless link, packets can be lost. so if you can not afford loosing packets you should implement an acknowlegdement/retransmisison scheme in your applications

Br,

Mads

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