Saturday, January 31, 2015

Somewhat broken...

I flashed a couple of changes to the device during the week.  Somewhere in that time I lost most of the sensitivity.  Call me paranoid but I suspect there are some undocumented features at work here, such as:
- CC2500 needs a power cycle to reset it ? (Like blue smirf)
- Library changes don't always get picked up by Arduino (like Wixel)

I had RSSI in the -50's, now they're in the -70's.

Originally I had the bare minimum for register settings, then I slowly added additional ones.  Living life in 5 minute increments.  Biggest improvement was setting the bandwidth slightly below the 335 khz that Dexcom wants.  RFStudio will choose a value of 400 khz, the other increment available is 325.  325 made a huge difference.

So, I'm back to the minimum and testing one value at a time.

On another note, I bought one of these:

This will allow me to experiment with Central role BTLE.  And, someone has cracked the Nike Fuel band, See->

This might make a good display device, and it appears to take a bitmap for that display, like the MetaWatch.  So maybe, we can talk directly to it and leave the Phone at home.

News alert, RSSI's back in the 60's, just by changing the "TEST" registers.  Isn't that great, if you call something "TEST", should it have any real purpose? Noooooo.  Thank you TI.

Almost time to head to the gym to hit people.  My best test environment.  Something there shuts down the Dexcom (antenna symbol) and my custom devices.

Saturday, January 17, 2015

Finishing this one up

Printed case view from the slicer.  I got lucky today, I was able to change the filament without having to disassemble the print head, small miracle.

Theory is, these will slide together and I'll add a little hot glue to hold it all together.  Real close to encasing this one in epoxy, but I'd like to find a way to cut down on static first.

Assembling the PCB didn't go quite as well as I'd hoped.  The CC2500 has a large(ish) crystal on the back (this is how they can sell for <$5).  I had to carve out a hole in the board, which required I add another jumper.  I knew I was going to route a slot, I just didn't realize how large it was going to end up being.

Here's a view of the completed board, with the separate lipo charger.  I usually mount the lipo unit on the same board, but I realized I could get this one really small if I did without.

Here's a view of the carving on the back of the board to allow the CC2500 to sit flush.

The CC2500 didn't work initially either.  I had to reheat all the connections, and the ones on the RFDuino.  Then I used a solder wick to remove excess solder.  After a few rounds, everything was working.  This just goes with the territory when you're hand soldering surface mount components.
I have an electric frying pan and solder paste, I may give that a try next.

And finally, most of my models since last January.

Friday, January 16, 2015

Thin is in

Test layout of parts on new PCB design.  This will be the first without a wixel.
Finished thickness should be 0.45" including case.  As I'm typing this, I realize I can get down to 0.4" if I do a cutout for the battery.   Finally gets me thinner than the dexcom, which is 0.5".

Kills me to have to leave a header on the board for programming and charging, could cut 0.4" off the length if I could do something different.  

This will be very pocket friendly.