"Since Google glass opened the door of wearable devices, a variety of" tease you "and" wearable devices have emerged in endlessly. Not long ago, the author accidentally got a flashclip, a wearable device sports tracker. I thought I had stepped into a fashionable and tall line at once. Unexpectedly, I was really tied up in a cocoon and thoroughly experienced self stupidity and self pleasure. No more nonsense, just look at this funny thing.
Flashclip appearance
This sports tracker, whose scientific name is flashclip, comes from an innovative technology company in China and is mainly used for counting steps at ordinary times. In terms of workmanship, the feel is OK, and it's not awkward to wear. The milky white rubber jacket clip is wrapped with flashclip. The holes on both sides of the rubber are said to adopt a unique shark gill design. However, in my opinion, this design is really not good. It's a model of Huangpo selling melons. You know, if you don't understand this design concept in advance, The first time I saw it, I thought I was accidentally poked several holes by a hard object. It was neither beautiful nor practical. It was a bit of painting snake and foot.
The rubber clip jacket can be removed. After taking it off, you can see the four metal contacts on the back of flashclip, corresponding to the special customized USB cable, which can realize the functions of charging and data transmission, as shown in the following figure.
Flashclip accessories
The only key of flashclip is the small black circle on the front, which mainly has two functions:
Short press to wake up the screen display and switch the display including step counting, calories consumed, health value and time (see the figure below)
Long press is the Bluetooth pairing connection with the IOS mobile phone and iTouch (note that it is only limited to these two devices)
Flashclip step counting, calories consumed, health value and time display function
Flashclip is easy to use
When you first see the flashclip product introduction, you will be surprised at its intention. It can support desktop client and IOS system app at the same time. However, if you understand the usefulness of these two software, you will find that you are really stupid and naive, which is definitely different from your original idea, or quite different.
The use of flashclip does not depend on the software application. The most important role of the client or app is to set the user's Daily "exercise amount" at the beginning, write the set target "exercise amount" data into flashclip and save it, and then you can wear and use flashclip purposefully, such as failing to meet the set calorie consumption demand at a certain time of the day, This gadget will vibrate to remind you that it's time to exercise. That's all. It's a bit like an alarm clock. Next, the author will use the desktop client to demonstrate how flashclip should face the first operation.
Flashclip is very simple to use. Wearing it can realize the only and only function - counting steps. Before using it for the first time, we first need to set an exercise goal for ourselves, open the flashclip official website, download a client installation called flash point, register an account, and bind the registered account with the flashclip you use.
After that, the process is simple. Remove the flashclip jacket clip and insert it into a special USB cable to connect to the computer. The desktop client that opens the flash point will display the data synchronized with the flashclip you use. After the synchronization is completed, the setting interface appears, including daily goal, filling in your own data, time and date setting, use setting and restoring factory settings, Basically, what is useful for us is the target value setting of exercise in this daily goal, as shown in the following figure
Flash client settings
The reminder function in the figure is that the daily exercise volume (steps are not enough) does not meet the standard at this time. Flashclip will vibrate and prompt you, but this function is somewhat retarded. The time point cannot be set by itself. Instead, it can only be set at several default time points or cancel the reminder, which is purely a decoration for comrades who work at 9:00 to 5:00 every day. Regardless of these, you can set them according to your needs and save them to complete the operation.
The use of IOS based app will not be repeated here, mainly because its function is the same as that of the client, but the connection between app and flashclip adopts Bluetooth pairing, and the function of APP only extends many reminders of eating, taking medicine, drinking water and other functions on the basis of the client function. You know, I'm sorry to describe these functions, I'm not afraid everyone misunderstood that this is an alarm clock.
So in the final analysis, flashclip has and only has such a function - counting steps. Moreover, this function can be used without the client or app. During this period, normal walking or running can be guaranteed with an error of less than five steps within a hundred steps.
In addition to synchronizing the flashclip with the computer, the USB cable of flashclip can also be used as a charging cable (see the figure below), and the time of full charge is very short, only tens of minutes. According to the current output standard of 500mA of the USB port of the computer host, it is not difficult to find that the battery capacity of flashclip will not be too large, and the actual use time can reach about 3 days, Coupled with the daily motor vibration consumption, the power consumption control is very good.
The OLED screen of flashclip lights up and shows charging
As a wearable device with only a single step counting function, flashclip is indeed a bit shabby. In addition, there are no valuable ancillary functions for either the client or the app. Where is the price value of up to 300 RMB? You might as well dismantle it!
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Flashclip disassembly
Although flashclip really doesn't have a function worthy of our joy, its high price makes the author very curious about the product design scheme. It's so expensive. Is it just a gimmick relying on Intelligent wearable devices? Or is it true that the hardware solution has another universe and equal value? Let's have a look.
Flashclip is very difficult to remove without violence. It took nine cattle and two tigers to pry open the back cover. It was so broken that it was fixed directly with glue. It's really cruel.
Open the back cover to see the exposed 3.7V, 60mah rechargeable lithium battery and a patch vibration motor. Continue to disassemble. Based on the previous experience, the rear shell should also be fixed with glue with the front panel, and the rear shell can be removed by gently cutting the gap with the knife surface
Disassemble flashclip1
It's really amazing. At first glance, the design layout of the motherboard is quite good. Take out the motherboard and you can see the OLED screen and membrane keys on the back. It seems that there is a ceramic antenna on the left side of the OLED screen. If nothing happens, it should belong to Bluetooth.
Disassemble flashclip2
The screen and battery are too lazy to be disassembled. After disassembly, we can basically find out the whole design scheme of the motherboard. If the OLED screen is opened, some test points hidden under the screen on the board can be found. It is not difficult to infer from the marked text that they are mainly the test points of SPI and microcontroller serial debugging interface.
Disassemble flashclip3
The focus is on the back of the OLED screen. The tightly arranged IC devices constitute the overall design scheme of the flashclip motherboard
Disassemble flashclip4 (click to enlarge it more clearly)
In the process of using flashclip, we have been familiar with its basic functions and can roughly understand the basic components of its circuit. This will let us take a closer look at the circuit design scheme on the flashclip motherboard.
Detailed solution of flashclip scheme
Microcontroller efm32lg330f128
I believe that most netizens who are not deep in the field of low power consumption feel strange to this efm32lg330f128 microcontroller with Gecko logo. The author simply explains its background. Efm32 microcontroller is developed by Norwegian energy micro company. It is a manufacturer committed to the field of ultra-low power consumption MCU, which is still very famous in the field of low power consumption.
Back to the microcontroller efm32lg330f128, it is equipped with 32-bit arm Cortex-M3 core, innovative low-power technology, supports fast wake-up from power-saving mode and integrates many optional peripheral resources. It is very suitable for battery powered mobile device systems requiring high performance and low power consumption. The system block diagram of efm32lg330 microcontroller can be referred to the following figure.
System block diagram of microcontroller efm32lg330f128
Microcontroller efm32lg330f128 on chip resources:
Based on arm Cortex-M3 core, it supports up to 48mhz dominant frequency, integrates 128KB flash, 32KB ram and qfn64 package
The flexible power management system has only 1.1ua Current @ 3V in the deep sleep mode of keeping RTC, ram and CPU running
It can expand 52 GPIO ports, 12 channel reflex peripheral system, 12 channel DMA controller, hardware AES, timer / counter and backup power supply
Communication interface: three general synchronous / asynchronous transceiver interfaces (SPI / IrDA / I2S, etc.) UART * 2, I2C * 2, USB2.0 host & OTG
12 bit 1m sampling / s ADC, 12 bit 500K sampling / s DAC, analog comparator * 2, operational amplifier * 3, power supply voltage comparator
Low power sensor interface (lesense): extensive sensor support, which can realize sensor monitoring autonomously in deep sleep
Single power supply 1.85 ~ 3.8V, 2-pin serial debug interface, 1-pin serial observation and other functions
From the parameters, it is easy to find that efm32lg330f128 is a powerful low-power mixed signal processing microcontroller, but it also has its own distinctive characteristics. The unique 12 channel reflex peripheral system (PRS) is a network that can directly connect different peripheral modules without CPU, and the peripheral module that sends reflex signals is called "producer", PRS will transmit these signals to the peripherals called "consumers", which greatly reduces the CPU wake-up time and thus reduces power consumption.
The DBG debugging interface of efm32lg330f128 microcontroller integrates ETM module, supports data information tracking, and supports 2-pin serial debug interface and 1-pin serial observation function. It is very practical in the product development stage.
Of course, in this flashclip product, the lesense interface of the microcontroller efm32lg330f128 is undoubtedly very important. This is a low-power interface for the efm32f330 microcontroller to realize configurable sensor detection by using on-chip peripherals, which can complete the measurement and processing of external sensor input signals without CPU intervention.
From the characteristics of this microcontroller, we can clearly feel the meaning it conveys - a low-power system with low power consumption and flexible setting everywhere, which can be flexibly customized in the actual product, close unnecessary peripheral resources, and achieve the purpose of reducing power consumption.
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Three axis acceleration sensor adxl345
ADI's three-axis acceleration sensor adxl345 is the main hardware part of flashclip to realize the step counting function. It has built-in ADC conversion and the maximum resolution is 13. There is no doubt about its importance in flashclip products. We know that early pedometer products often used weighted mechanical switch to detect the pace, and equipped with a simple counter. Shaking this device is like a pendulum swinging back and forth to hit the stop to achieve a simple step counting function.
The adxl345 triaxial acceleration sensor adopts a complex polycrystalline silicon surface micromachining structure. It can measure the static gravity acceleration in tilt detection, as well as the dynamic acceleration caused by motion or impact, with a measurement range of + - 16g. In flshclip, MEMS (micro electromechanical system) inertial sensor and complex software are used to accurately detect the real pace, It has more accurate step detection and lower false detection rate.
Another feature of adxl345 is its ultra-low power consumption. Its proprietary on-chip 32 level first in first out (FIFO) buffer can store data (collected points) and perform relevant operations of pedometer applications, so as to minimize the intervention of the main processor and save valuable system power for portable devices. In addition, the adoption rate of ADC can be reduced through software setting to enter a lower power consumption mode. In the automatic sleep mode, the power consumption lower than 12.5hz data rate is usually only 23ua. In the actual product design, the connection can be established with the microcontroller through I2C or SPI digital communication protocol interface. See the adxl345 system block diagram below
Adxl345 system block diagram
Bluetooth 4.0 low power chip em9301
Recently, Aiban has also dismantled many products based on Bluetooth 4.0 low-power chip design schemes. Most of them basically adopt Ti, nodic and CSR single-chip solutions, which are different in flashclip. Because we see the powerful microcontroller efm32 from the design scheme, there is no need to adopt Single chip Bluetooth solutions are also not recommended.
In fact, the Bluetooth solution on the flashclip pedometer adopts the Bluetooth 4.0 low-power chip em9301 of EM microelectronics. EM microelectronics is a semiconductor company under Swatch Group and a major supplier of analog and mixed signal semiconductors in the field of ultra-low power applications.
In actual products, em9301 has two versions, namely, the 1.5V working voltage version with integrated DC / DC boost conversion and the 3V working voltage version without DC / DC conversion. The em9301 on our flushlip motherboard does not have DC / DC boost conversion internally, and is powered externally by a 3.3V output LDO, and the enabling pin of the LDO is controlled by the microcontroller efm32lg330f128, In other words, the LDO that usually supplies power to the Bluetooth chip does not work. When Bluetooth needs to be used, the microcontroller controls the LDO to output 3.3V voltage to supply power to em9301, which greatly reduces unnecessary power consumption.
Em9301 internally integrates a single Bluetooth 4.0 low-power controller, which has the characteristics of low voltage and low power consumption, and integrates host control interface (HCI), which establishes a complete system by connecting with external MCU
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