EEVblog #412 - Jawbone UP Pedometer Teardown  - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: January 19, 2013, 09:27:03 pm
content: What's inside a Jawbone UP Pedometer?MSP430F5548:http://www.ti.com/product/msp430f5528BQ24230:http://www.ti.com/product/bq24230MX25L8006E:http://www.zlgmcu.com/mxic/pdf/NOR_Flash_c/MX25L1606-8006E_DS_EN.pdfDave.

author: janekm
author_rank: Unknown
timestamp: January 20, 2013, 01:23:37 am
content: The accelerometer is almost certainly the black part on the back of the processor board. It seems to be about 2x2mm which given when the UP was designed would suggest one of the Bosch Sensortec parts as they were the first out in that size (they now do a 1.2x1.5mm one, crazy!)

author: andyturk
author_rank: Frequent Contributor
timestamp: January 20, 2013, 01:43:44 am
content: I'm curious as to why folks continue to use MSP430s in these things when ARM M0 chips would (presumably) provide the same power and form-factor characteristics without having to screw around with a 16-bit architecture.The Jawbone probably doesn't need a lot of software to do its thing, but there are other super-tiny products (e.g., FitBit and Lark) that have Bluetooth connectivity, requiring lots of code for the BT stack. I think both FitBit and Lark use MSP430s too.What's the special MSP430 sauce that keeps getting design wins?

author: kyndal
author_rank: Regular Contributor
timestamp: January 20, 2013, 02:27:15 am
content: Quotethey are usually pretty cheap..i like the msp430 series./Kyndal

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 20, 2013, 09:52:18 am
content: QuoteWhen you're writing in C, the underlying architecture is of minimal significance unless you have high performance requirements.Peripherals, power management, pricing, availability, package options and familiarity with peripherals and devtools are generally much more important considerations.

author: andyturk
author_rank: Frequent Contributor
timestamp: January 20, 2013, 01:49:18 pm
content: Quote from: mikeselectricstuff on January 20, 2013, 09:52:18 amExcept when the underlying arch runs out of address space, then it becomes a pain in the neck. It's not really an issue for data/RAM, but it's getting easier to fill up your flash with networking code (e.g., BlueTooth, USB, TCP/IP, etc.) leaving little room for what actually makes the product valuable. For example, I tried putting an open-source BT stack on an MSP430 almost a year ago and nearly blew out the 64K address space before I got to add any application code. The 20-bit mspgcc implementation was still a little raw at that point, so I hopped over to Cortex M3 and never looked back.Your points about pricing, packaging and "familiarity" are right on though. I suspect that most embedded engineers have more toolchain allegiance than code monkeys (like me) do. The proprietary toolchains make the segmented problems mostly disappear.Another example of sorts is the Nike Fuel band you tore down a while back (I just watched the video again today :-). It has both an MSP430 *and* a low-power Cortex M3. Interestingly, the MSP430 is located right next to the BlueTooth tranceiver and I suspect the only thing that the TI part is doing is running a BT stack, with the ARM chip left to implement the "algorithm".The STM32L family has more than enough juice to run a BlueTooth stack and the application code, but I think the lack of a qualified BT stack (for the M3) was the issue there. The hardware would certainly be cheaper with only one mcu, but that would require the stack vendor to port and/or open up their code to other architectures, which the vendor might have been reluctant to do.You'd think that it'd be hardware driving the big design decisions for these products, but it seems like software (e.g., toolchains and networking stacks) is just as important.

author: janekm
author_rank: Unknown
timestamp: January 20, 2013, 03:12:10 pm
content: Quote from: mikeselectricstuff on January 20, 2013, 09:52:18 amActually, last time I checked MSP430 is pretty terrible for pricing, availability, and package options (at least those are the reasons that made me move away from them). There was very little pin compatibility between parts, and say finding one with a multiply unit in the package size I needed was impossible. But the Cortex-M0+ parts weren't out yet when the Up was designed (mind you, some of the M3 parts are more than competitive with MSP430 anyway), and I suspect one factor in the choice for the Up is that the MotionX algorithms they use appear to have a MSP430 implementation as standard. Also, TI have been good for providing very small, low power dev kits for the MSP430 that have become very popular for developing low-power wireless devices.

author: NiHaoMike
author_rank: Super Contributor
timestamp: January 21, 2013, 04:23:58 am
content: How is it charged? Do they use the mic bias or line outputs as a power supply or is there another connection?

author: SeanB
author_rank: Super Contributor
timestamp: January 21, 2013, 04:48:31 am
content: I would guess the 4 pin 3.5mm plug goes into a socket that adapts it to USB, and it charges from the usb.

author: PA0PBZ
author_rank: Super Contributor
timestamp: January 21, 2013, 04:56:13 pm
content: In the box•UP band•Quick start guide•USB charging cable

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: January 21, 2013, 06:22:10 pm
content: I bet most of these toys end up in junk box in 1-2 weeks after purchase or as soon as novelty factor runs out. Looking into my junk box I see some kind of Sony media player that looks like a small tube with a rubber strap, handheld TV receiver (1999, or 2000?), some kind of electronic watch, 3 cell phones, some kind of PDA ... Every time I see new useless toy I like to look into that box to remind myself that new, very cool looking thing I am so excited about, will be in this box in 2 weeks max. Yet somehow some companies still manage to convince us that we really need one more useless gadget for $99.9999999.....I do admit that designing and building something like this is x10 more fun than buying and using it :-).

author: yarfi
author_rank: Newbie
timestamp: January 29, 2013, 01:00:17 am
content: Hey Dave, I was wondering if the tactile button on the end of the UP was able to be re-attached once you removed it. The video seems to skip over the actual removal of the button. Was it glued on and thus loses its adhesion or does it clip back on? I want to take the button off of mine but want to know how it attaches first. Thanks!

author: aryajur
author_rank: Newbie
timestamp: January 29, 2014, 06:43:09 pm
content: The BQ24230 is a 4.2V battery charger while the battery in the teardown shows its is 3.7V. Is it possible it is one of these:BQ24261 -http://www.ti.com/product/bq24261BQ24297 -http://www.ti.com/product/bq24297BQ24295 -http://www.ti.com/product/bq24295

author: HKJ
author_rank: Super Contributor
timestamp: January 30, 2014, 02:52:43 pm
content: Quote from: aryajur on January 29, 2014, 06:43:09 pmA 3.7 volt nominal LiIon cell must be charged with a voltage of 4.2 volt.

author: aryajur
author_rank: Newbie
timestamp: January 30, 2014, 08:39:11 pm
content: Quote from: HKJ on January 30, 2014, 02:52:43 pmThanks for this information. So there must be an on board regulator as well (probably an LDO) since the MSP430 can only work up till 3.6V VDD