From the Lab ...

... Hacking and Slashing since 2002

So I have (had?) a few (6+) of the older nRF51822-EK dongles hanging around the shop, and was recently using one related to some BLE sniffer hackery (more on that later). As I was getting the code running, I noticed that one of the timers (Timer0) was acting peculiar. No matter what bitmode I set the timer to, it was always counting in 24bit mode ... long story short, I was directed to this - https://devzone.nordicsemi.com/question/1310/nrf51822-bit-width-and-bitmode/ Basically Timer0 of the rev1 and rev2 Si of the nRF51822 was broken. So, what does any good engineer armed with a shop full of expensive re-work equipment do ... re-work. 
 
I removed the nRF51822 Si off these and replaced them with nRF51422 QFAB A1 (rev3) Si ... works(ed) like a charm. I do have access so several nRF51 Dongles (newer style), but why throw these way when they can easily be updated. The only difference between the '822 and the '422, is that the 422 supports ANT (along with BLE). 
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Funny. Looks like there were a few nRF52s (nRF52832 QFAA AA) in there. I had 2 nRF52 Preview Development Kits that had engineering samples of the nRF52 on them. Again, why throw them out when they can be easily updated with new Si. 
 
A little closer ... 
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Speaking of CES2017 and all of the Apple HomeKit - kit, here is an older device for your viewing pleasure the HomeKit compatible iDevices Switch. I picked these up at Home Depot this past fall on clearance. Three were purchased for $13.03 (from $49.99) and one was purchased for $0.01 - that's right, I purchased one for a penny. 
 
Side story about Home Depot clearance pricing - when a product reaches $xx.03, it's essentially gone (or going to be gone very very soon). At the next markdown interval, the store reset team marks them down to a penny and that is managements cue to literally clear them out (as in one destination is the trash). I "caught one" still on the shelf that showed $13.03, but the computer had already marked it down to $0.01. SWEET! 
 
Without further delay... 
 
Box. 
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Markdown price for 3 units... 
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Guts. Pretty sure the smt IC in the lower left is an Auth IC. Seems to have numbering that I recognize (For complete disclosure, I have a license, but I don't divulge details). A few Broadcom parts. 
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After the teardown, I'm not sure how I feel about this unit. Seems to be very well built, which is good ... however, can a thing be too well built? 
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So I purchased 2 of these units on eBay [I think I paid $30-ish each ... the ~$150 "normal" price tag is crazy] to tear one down to see what they used for the BLE comms. Unsurprising that they used the NRF51822 (QFAA H0 - Rev 3 Si) ... what was curious was the use of the AFE4400 from TI. If the development company had used a different sensing element (say an Si114x series from Silicon Labs), they would have had a less-expensive / less-complicated straight forward design. Oh well, they didn't ask us.  
 
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Here is the basic photodiode-with-2-wavelength-leds setup... 2 LEDs to generate the 2 different wavelengths for pulse oximetry. One LED emits visible red light (typically around 600nm), and the other LED emits near infra-red light (typically around 900nm). Interesting that they appear to use a thermistor to see if the sensor is still on the child's foot.  
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And, this is what is typically used in a hospital environment (sans finger wrap) ... The LEDs are contained within one package shown on the left (as you forward bias the device, you get one wavelength, and if you reverse bias it, you get the other). 
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Did you know that the Misfit Flash has an nRF51822 device at it's heart? I do. And when repurposed, they make great little devices for beacons, or temp monitoring, or acceleration measurement (via the built-in LIS2DH), or a single button remote, etc. Here are a few pics ... I'll try to include the code and pinouts (for the LED's / switch / accelerometer) at a later date. 
 
Anyone know why there is the symbol for "Sputnik" on the silkscreen? Just curious... 
 
 
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So, for the past 6 months (from Feb. '16), I have been successfully using Xcode as my development environment for ARM cortex-mX devices (mainly cortex-m0). 
 
August '15 I finished creating an Xcode platform for ARM devices copied from the existing iPhone platform (with additional inspiration from Appportable's Android development platform for Xcode) ... unfortunately, it doesn't do native (meaning built-in) debugging. This is primarily for 2 reasons - 1) I haven't figured it out ... yet. But I WILL. And 2) The JLink tools require the use of GDB instead of LLDB, causing all sorts of headaches getting GDB running in the latest edition(s) of Xcode. Again, I WILL solve this. For the time being, I'm using the Segger JLink Debugger app; it's OS X native, and is scriptable, so it can be called from Xcode. 
 
If you would like more information, or have suggestions on how to fix the GDB / JLink problem(s), drop me a line. 

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