Hi Richard, Just so you know (for future reference), in BoilerPlate the start_value is set to 1 because the msp430 can only write/read 16-bit words to/from even addresses. In the data packet there is a one byte packet_type field before the first 16-bit value (the time-stamp).
Mike On Tue, Jun 14, 2011 at 5:10 PM, <[email protected]> wrote: > Hey Mike, > > I took your suggestion and things pretty much worked out (: It turns out > that in boilerplate the start_value is set to 1 since data_packet_size is > hardcoded to be 25, whereas my packet is only 10 bytes, so things got > shifted which is why there was a zero column. So what you said was about the > conversion is right, given that the data is read correctly. The reading part > was as you said as well, given that the storage buffer does not change in > the time period, the data gets bunched up together waiting to be read. > > Thanks a lot for your help, > Richard > > > > Quoting mike healy <[email protected]>: > > Hi Richard, >> >> The answer to your question will depend on how you are creating the >> Bluetooth packet on the Shimmer. Also the method you are using to "convert >> the data to uint8" in Matlab will be relevant. >> >> The processor on the shimmer is little-endian. So, unless you are >> manipulating data on the Shimmer, the first 8-bits (1 byte) received of >> the >> 16-bit number should be the least significant parts, and the second byte >> is >> the most significant part. This is how ShimmerConnect handles the received >> data. In which case when you say you are "multiplying the 7th column by >> 256 >> and adding it to the 8th", this should really be the other way around (but >> then this will depend on how you populated the "columns", as the data >> you're >> shown below doesn't support this). >> >> Anyway, the easy way of figuring this out is to just hard code some values >> in the Bluetooth packet on the Shimmer, and manipulate the data in Matlab >> until you get these values back out. Of course use different values for >> each >> (simulated) sensor reading, so you can correctly figure out how the >> different sensors split up. >> >> Also as for your fread question, I would guess that a call to fread will >> read X (in your case 1000) values from the serial buffer. Then when you >> call >> it again it will read the next X values from this buffer. As for whether >> or >> not it is the 1000 currently being transferred, this will depend on the >> size >> of the serial buffer. >> >> Mike >> >> >> >> On Mon, Jun 13, 2011 at 8:24 PM, <[email protected]> wrote: >> >> Hi, >>> I'm working with the shimmer ECG module and trying to add bluetooth >>> functionality to JFATlogging. I'm getting the data stream through fread >>> in >>> matlab and converted it to uint8 as such: >>> >>> 6 201 4 203 7 226 7 0 8 0 >>> 6 220 4 225 7 215 7 7 8 0 >>> 6 195 4 214 7 222 7 253 7 0 >>> >>> which presumably are 5 channels split into two bytes each (7&8th column >>> being ECG). So i'm just multiplying the 7th column by 256 and adding it >>> to >>> the 8th, which is the same operation as the shimmerconnect code, however >>> the >>> data looks much wonkier than if I just plotted the 8th column alone. Any >>> ideas on how to process these numbers? >>> Also, I'm calling bluetooth.write after every DMA0transferdone, which may >>> or may not take place depending on send_ready being reset in >>> bluetooth.writedone, which seems to cause the data to be sent in >>> irregular >>> intervals (I've excluded the timestamp in the datapacket)? >>> >>> Lastly, just a general serial port question: every time I call fread to >>> take in a stream of say 1000 numbers, is it the next 1000 numbers from >>> the >>> last time i called fread, or is it the 1000 currently being transfered as >>> soon as I called fread? >>> >>> Thanks, >>> Richard >>> >>> _______________________________________________ >>> Shimmer-users mailing list >>> [email protected] >>> https://lists.eecs.harvard.edu/mailman/listinfo/shimmer-users >>> >>> >> > > >
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