"Wearable device is one of the hottest words at present. This wearable device concept integrating" hardware, software and cloud "makes people aware of a novel, fashionable and intelligent interaction mode, and has become another competitive field for manufacturers in addition to smart phones.
Smart bracelets, smart watches, smart glasses... Wearable devices emerge in endlessly. At present, this field is still in the primary state of savage growth. Of course, the opportunities are endless. All kinds of entrepreneurial teams and solution companies show their abilities, and some big manufacturers are eyeing them. As the market is not mature, the division of labor is not very clear. Companies that have entered need to take into account all aspects of design, production and sales. From the perspective of trend, the establishment of platform, whether software platform or hardware platform, is a very good entry point. Giants in many industries have begun to deploy, and MediaTek is one of them. I believe many people know that MediaTek's "turnkey" model will greatly ripen and sweep a market, and this time it even set up a "MediaTek creative laboratory" to provide comprehensive support.
MediaTek labs is to help product developers with different backgrounds and technical levels accelerate the development of wearable and Internet of things devices. It plans to provide global developers, makers and service providers with comprehensive support in software development kit (SDK), hardware development kit (HDK), technical documents, technology and commerce. Its first project is the linkit development platform, which mainly covers four parts (as shown in the figure below):
MediaTek aster (mt2502) SOC is the smallest commercial SOC in the world in the field of wearable devices
Linkit OS, for mt2502, is an operating system for wearable devices or Internet of things devices to connect to other intelligent devices or directly connect to cloud services
Linkit HDK is a hardware development tool based on mt2502. At present, it mainly provides linkit one development board for silicon delivery technology
The linkit SDK, a software development tool, includes a plug-in to the Arduino IDE, a linkit API function library, and a development board firmware update tool (elipse ide will be supported in the future)
Linkit development platform
After learning about the linkit development platform, it's time for today's protagonist to appear - the linkit one development board.
Linkit one development board
Linkit one development board is an open source hardware jointly launched by seeed studio and MediaTek. I believe that after understanding MediaTek's linkit development platform, we are no longer confused about linkit one. Based on MediaTek's aster (mt2502a) (mt2502 Data Book) ASoC processor, linkit one integrates high-performance Wi Fi and gpsx chips. At the same time, linkit one provides an interface compatible with Arduino uno, which can easily intervene in various shields and sensors. First, let's take a look at the true face of linkit one Lushan.
LinkIt ONE
Linkit one accessories include:
Linkit one development board * 1
GPS antenna * 1
GSM antenna * 1
WiFi / BT antenna * 1
1000mah lithium battery * 1
At first sight, linkit one will only think of being small and concise, which has nothing to do with "powerful functions". Then the fact is that linkit one arranges the core devices on the back of the board, which gives people an illusion.
Linkit one has rich functions. It is not only compatible with the current popular Arduino uno R3 interface in the design of the development board (there may be some differences in actual functions, which will be introduced later), but also can easily transplant the existing rich routines of Arduino for development, reduce the learning cost, and integrate the current popular GSM / GPRS in the field of intelligent wearable devices and the Internet of things WiFi / BT, GPS and other wireless communication functions. In addition, it is worth mentioning that the accessories provided by linkit one also include a 1000mah lithium battery, which can facilitate mobile development and testing. For engineers who like DIY, the power supply problem when developing products based on linkit one prototype board has also been properly solved.
Linkit one onboard resources
Although the on-board functions of linkit one are very rich, the actual size of the board is only 3.3 * 2.1 inches, which is about the size of the Arduino development board on the market. The front layout of linkit one board is very simple. There are only some commonly used peripheral interfaces and function switching switches. The core IC devices are concentrated on the back of the board, as shown in the figure below.
Linkit one development board
Linkit one parameter:
Master control: mt2502a (aster, ARM7, ej-stm), 5.4mm * 6.2mm, 143 ball, TFBGA package
Main frequency: 260MHz
Size: 3.3x2.1 inches
Flash: 16MB
RAM: 4MB
IO port output current: 1mA
Number of analog ports: 3
Digital output level: 3.3V
Input voltage of analog port: 5V
Serial port: soft serial port and hard serial port (Serial1, d0 & D1)
SD card: up to 32g (class 10)
GPS(MT3332)
GSM: 850/900/1800/1900 MHz
GPRS: Class 12
Wi-Fi: 802.11 b/g/n
Bluetooth: br / EDR / ble (dual mode)
The core devices on the back of linkit one are covered by a shield, accounting for more than 2 / 3 of the whole board area. Only one card holder compatible with the functions of microSD card and SIM card and three antenna RF interfaces (GSM / WiFi / GPS) can be seen outside. After opening the shield, you can clearly see the layout of the board circuit. Relying on the perfect solution of MediaTek and the ultra-high integration of mt2502a, the realization of wireless communication functions such as GSM / WiFi / GPS only depends on several core devices such as mt2502a + rf7198 (RF power amplifier) + mt5931 (WiFi) + mt3332 (GPS), Moreover, mt5931 (mt5931 data manual) and mt3332 (mt3332 data manual) are also the solutions of MediaTek. These devices are not introduced here. If you are interested, you can refer to the specifications of these products. The following figure is a simple peripheral resource block diagram based on mt2502a SOC, which can clearly understand the powerful and rich function integration of mt2502a.
Simple functional block diagram of mt2502a SOC
MediaTek mt2502a SOC characteristics:
The smallest commercial system level chip in the market (5.4mm * 6.2mm)
CPU core: ARM7 ej-s, the main frequency is 260MHz
Memory: 4MB ram, 4MB flash memory
Dual Bluetooth, 3.0 and 4.0 low power stack
GSM and GPRS modems
Power supply: PMU, charger and other functions, low power consumption mode with sensor hub function
Multimedia: audio, video, camera
Interface: used for LCD, camera, I2C, SPI, UART, GPIO and other external ports
As a SoC for wearable devices, the rich functions of mt2502a are really amazing. It integrates power management, Bluetooth, processor, ram and other functions. This is an entry-level mobile phone SOC scheme. Indeed, if you review the development history of MediaTek, You will find that designing such a wearable device SOC is really a piece of cake for MediaTek. You can "modify and decorate" the mobile phone SOC in the 2G era. In addition, for the wearable device scheme, the package size is a crucial factor, which affects the product appearance size, structure layout, etc, The mt2502a SOC integrates so many functions on this chip with a size of only 5.4mm * 6.2mm. It is believed that only with the advantage of packaging + function, MediaTek can let competitors drink a pot, not to mention the low-power characteristics that MediaTek SOC has always been proud of.
The function, integration and power consumption of mt2502a can be said to be perfect for the wearable device scheme, but similarly, some details of the implementation of each function are different from our usual usage habits (especially the engineers who are used to microcontrollers), such as the linkit one development board "compatible with Arduino uno R3 expansion interface" mentioned earlier, People subconsciously think that each IO can be used like Arduino, but the fact is that mt2502a is different from Arduino in the functional implementation and electrical parameters of some IO ports, especially in the design. For specific differences, please refer to the following table
Some interface differences between linkit one and Arduino Uno
After understanding the functions and parameters of linkit one board and mt2502a, I believe many engineers are full of expectations for the application of products based on mt2502a SOC. In fact, products based on mt2502a have appeared on the market, such as the smart watch omate x below. If you met mt2502a, what kind of products would you design?
Power on use
For the use of linkit one board function, we will further understand it through the actual power on test. Of course, the preliminary preparations are essential:
Install the development tools of Arduino ide version 1.5 or above
Configure MediaTek SDK based on Arduino IDE
Install USB debugging driver and virtual serial port driver
These software packages can be found in the Creative Laboratory of MediaTek, but one thing to pay attention to when installing the USB driver. After installing the driver, you can see two serial port displays, as shown in the figure below
These two serial ports represent different functions, among which
MTK USB debug port: debug serial port for downloading programs
MTK USB modem port: the virtual serial port is used as the serial port data printout port
In the previous evaluation or disassembly articles of aiban.com, we rarely touch the GSM and GPS functions in the linkit one development board, so next we mainly experience the use of these two functions.
GSM function
In the GSM function test, we are going to do a function to control the LED lighting through SMS messages, which involves a practical design problem. According to the IO port parameters of mt2502a, the driving current is very small (0.3 ~ 3mA), so it is impossible to directly drive the LED lighting. Therefore, we need to control it through a triode, and the driving signal is set to D3 pin; Moreover, the GSM function requires the SIM signal. According to the data of linkit, we can find that the SIM card signal is multiplexed with the SPI signal. Therefore, switch the switch on the front of the board to the SD / SIM position. The physical connection diagram is as follows
Drive LED circuit
After downloading the program through Arduino IDE, you can see the prompt of "GSM OK" through sscom32 serial port tool. At this time, you can send a short message to the SIM card of linkit one card through your mobile phone, you can see the caller ID number and control command on sscom32, and control the LED on or off by controlling D3 pin, as shown in the following figure
Control of led through SMS message
I believe this routine is just holding bricks and attracting jade. This is just the tip of the iceberg of GSM function. I believe there are more and more creative ideas waiting for you to develop.
GPS function
There are corresponding GPS routines in Arduino IDE, which we can use directly. After downloading the program, place the GPS antenna of linkit one in the window.
GPS routine use
Through the serial port tool, you can view the GPS information printed from the MTK USB modem port, but there is only one data output statement of gpgga. Although it contains UTC time, longitude and latitude, number of satellites, positioning status and other information, there is no statement output indicating the satellite carrier noise ratio, that is, it is difficult for us to accurately judge the positioning status at this time.
Of course, we can also use more intuitive software to view the positioning of GPS, such as visual GPS in the figure below
Get GPS serial port information
The altitude in the above figure refers to the height from the sea level, not from the ground at this time. We can input the obtained longitude and latitude information into Google map to view the corresponding location, as shown in the figure below
Actual GPS positioning
The green arrow is the actual positioning information, while the red dot is the position of the board at this time. It is not difficult to find that the positioning situation at this time is not very ideal, there is a large drift, and the serial port information can not know the carrier noise ratio of the satellite. It is a pity that the cause of the drift cannot be further analyzed.
After reading the introduction of linkit one development board, do you have the impulse to have a try? Compared with the microcontroller boards often evaluated by aiban.com, linkit one is obviously more attractive and has richer functions. Especially in the hot field of wearable devices, many functions integrated by linkit one and flexible wireless communication configuration are one of its killer Maces.
Summary
This paper introduces MediaTek's linkit development platform, linkit one development board and the powerful wearable device solution mt2502a SOC, which is compatible with the current popular Arduino interface and easy to transplant development environment. It integrates the hot wireless functions such as GSM / GPRS, WiFi / BT and GPS. Linkit one is like an entry-level smartphone platform, The rich expansion ensures the feasibility of various functions of engineers when developing products. MediaTek mt2502a SOC has achieved the necessary elements in the field of wearable devices in terms of function, power consumption and packaging as much as possible. With the advent of mt2502a (MediaTek's second-generation wearable solution mt2601 has also been exposed), I believe MediaTek should think about how to pull the partners of Google Android ecosystem to its own linkit platform.
reference material
Linkit one development board materials
MediaTek creative laboratory
Linkit one purchase link
Ardu
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