"Stm32f4 Discovery Series boards of STMicroelectronics based on arm cortex-m4 processor are usually famous for their multi-function and high performance. If you pay special attention, you will also find that stm32f4 series boards launched by St are basically equipped with their own sensors, such as sound sensors, motion sensors, acceleration sensors, etc, While promoting its own microcontroller, ST has virtually publicized its sensor series products. On the one hand, it benefits from the rich product line of Italian French semiconductor. On the other hand, with the inevitable development trend of wearable devices, it also shows ST's desire for sensor market share.
Recently, aiban.com got another stm32f4 Discovery series development board from Yifa semiconductor. The board is based on the stm32f429 microcontroller with a powerful cortex-m4 core. At the same time, it carries a very magical thing that jobs claimed when the iPhone 4 was just released - the three-axis gyroscope. Let's have a look.
STM32F429I Discovery
ST's simple packaging has already established the brand image of Discovery series. Without too much rendering, used friends can know whose product this is at a glance. This time, compared with the past, the board comes with a 2.4 TFT LCD, and the board supporting graphical output is believed to be very popular with users.
Stm32f429i discovery front
Stm32f429i discovery back
Stm32f429i discovery hardware principle block diagram
Stm32f429i discovery onboard resources:
Stm32f429zit microcontroller of STMicroelectronics, with built-in 2MB flash, 256Kb ram, lqfp144 package and 8MB SDRAM on board
Onboard st-link / V2 can debug onboard microcontrollers and external microcontrollers
Board power supply: supply power through 5V Mini USB interface or 5V and 3V external power supply
Italian French semiconductor triaxial gyroscope l3gd20
2.4-inch TFT LCD, 262K color RGB, 240 * 320 pixels, two mechanical keys - user, reset
6 LEDs - two user LEDs, one USB communication led, one 3.3V power LED, and two USB otgs LED (including VBUS and overcurrent LED)
The 4-layer stm32f429i discovery development board is at least very simple in appearance, which is different from the previous stm32f4 series boards. This time, because the front of the board is equipped with a 2.4-inch TFT LCD screen, the layout of the whole development board has changed greatly, and the microcontroller has been moved to the back, while the front is the consistent mechanical key and the very convenient on-board debugger st-link. You can also switch st-link to debug the on-board microcontroller or the microcontroller series of external STMicroelectronics through hat skipping. This is an additional benefit. Used friends must like this humanized function very much. By the way, the WiFi module provided by the popular mxchip intelligent hardware innovation design competition can be debugged with st-link.
Another important feature of St Discovery series cards is the led out IO port. On the stm32f429i discovery development board, we also see two rows of symmetrical needle row seats. St leads out the unoccupied IO ports of microcontroller through the needle row seat. On the one hand, the user's subsequent operations on the card, microcontroller evaluation and DIY, and the needle row seat can be compatible with the prototype board of STMicroelectronics, This is a small ecosystem exclusive to St.
Recommended development board
High performance stm32l152-eval development board based on arm Cortex-M3 core
Low power stm320518-eval development board based on arm Cortex-M0 kernel
In addition to the microcontroller, there is a special micro USB AB interface on the back of the board, which supports USB2.0 OTG function and can be connected to the slave device of USB flash disk mouse on the board. Looking at the boards, it is not difficult to find that the stm32f429i discovery board mainly reflects the biggest different function points from the previous F4 series boards, such as the integration of LCD controller and USB2.0 OTG, and the realization of these functions is due to this new microcontroller stm32f429zit6u.
Stm32f429zit6u microcontroller
Stm32f4x9 microcontroller system block diagram
Stm32f429zit6u microcontroller features:
Based on 32-bit arm cortex-m4 kernel, with FPU and art accelerator (supporting zero waiting for data in flash), the maximum frequency is 180mhz
It has built-in 2MB flash and 256Kb ram, which is the largest expansion in this series of microcontrollers, and supports 32-bit external storage at most, such as SRAM, PSRAM, SDRAM, nor / NAND flash, etc
It supports LCD parallel interface (8080, 6800 mode), integrated LCD-TFT controller, dedicated chrome art accelerator for graphics, and XGA resolution
Three 12 bit ADCs, up to 24 channels, two 12 bit DACs and 17 timers
Up to 168 interruptible IO ports and 21 communication interfaces (I2C * 3, uarst * 4, UART * 4, spi * 6, Sai * 1, can * 2, SDIO * 1) are supported
Integrated USB2.0, USB otg2.0, 10 / 100M Ethernet PHY, 8-14 bit camera parallel interface, etc
Compared with the few functions visible on the board, it is easy for unfamiliar friends to ignore the power of its core microcontroller, and the simple board design of St really keeps a low profile of stm32f429zit6u microcontroller, which is like installing a BMW engine on a tractor. How do you know its power if you don't try it.
The M4 core with FPU has its own unique market in the field of microcontroller. It can greatly reduce the operation time when processing floating-point operations, such as FFT, audio decoding and filtering operations, which is also the biggest difference from the microcontroller without DSP function. The stm32f429zit6u microcontroller based on the M4 core is hard enough (based on the M4 core and with FPU), and the unique art accelerator of STMicroelectronics can greatly reduce the time for the CPU core to access the flash memory, so as to achieve higher and faster code execution efficiency, which is similar to the Zhaoyi gflash technology previously evaluated by Aiban.
In addition to its strong performance, stm32f429zit6u microcontroller also has rich functions. Of course, it can not be reflected only from the board, which is a pity. We can see more functions of the microcontroller in the stm32f4x9 microcontroller system block diagram above, such as camera interface, serial port, network port, can bus interface, etc, On this fully functional MCU, its application has strong universality, ranging from simple human-computer interaction interface, instrument panel display and other applications to industrial control and other applications.
In addition to the powerful microcontroller, the stm32f429i discovery development board is equipped with its own three-axis gyroscope, which can be said to be another feature of the board. I believe it is also a function most concerned by many users interested in sensors.
Italian French semiconductor triaxial gyroscope l3gd20
Nowadays, the trend of wearable devices is really popular with all kinds of sensors. In addition, electronic devices are also flocking to sensors. For example, even entry-level mobile phones within a thousand yuan now have no less than 5 sensors, while the Samsung Galaxy 5, which was disassembled not long ago, has more than 10 sensors built in, In this paper, we don't investigate whether such an approach is meaningful, but the sensor market is really hot. ST is one of the most competitive manufacturers in the sensor market, and its sensor products include various series (see the figure below).
Italian French semiconductor sensor product series
Look back at the three-axis gyroscope l3fd20 on the stm32f429i discovery development board. It is a device for measuring angular velocity and maintaining direction. Its principle is based on the conservation of angular momentum. The sensing element and IC interface are integrated in l3fd20. The data output is through I2C or SPI digital interface, and the switching between I2C and SPI interface can be realized through chip selection signal, On this development board, the data of three-axis gyroscope is output through SPI interface. L3fd20 provides users with three optional different speed measurement rates ± 250 / ± 500/ ± 2000 DPS (degrees per second). In addition, l3fd20 also integrates a temperature sensor, which also facilitates the user's collection of temperature information. The whole l3fd20 adopts 16pin LGA package with a size of 4 * 4mm. It is very suitable for game and virtual reality input devices, motion control and MMI, machinery and robot applications.
If the boring data can't make you clearly understand what the three-axis gyroscope is, the author recommends that you can take a look at the application of the three-axis gyroscope demonstrated by jobs at the iPhone 4 press conference. By rotating and pulling away a long column made of wood blocks, you can well reflect the application of the three-axis gyroscope in practice. Coincidentally, the three-axis gyroscope in the iPhone 4 adopts the same st scheme, which reflects the quality of the Italian French semiconductor sensor on the one hand, and allows the majority of electronic enthusiasts to see that Apple's design scheme can be used. While the vanity is greatly satisfied, it also allows us to see that the original Apple's things can also be open source.
Stm32f429i discovery development board powered on
After reading the hardware part of the whole stm32f429i discovery development board, we then power on and start it. The board can be powered through the MINIUSB interface of st-link. Because the development board itself does not have a MINIUSB cable, you need to prepare one by yourself. OK, power on directly.
When the MINIUSB cable is plugged in, the red power LED and the red MINIUSB communication indicator light are on, the user LED3 flashes, and the LCD screen shows the loading state. In less than 2 seconds, it enters the humanized graphical interface (see the figure below).
Stm32f429i discovery development board powered on
In the stable standby state of the graphical interface, the CPU occupancy rate has been maintained at 2%, which is not too high. The six functions we can browse from the graphical interface include video, picture, clock, game, performance and system information. After a simple try, the author found that the main frequency of MCU marked in the system information is only 168mhz, which is different from 180mhz in product promotion. Is it limited by software?
I believe that everyone, like the author, is more concerned about the performance of the microcontroller. The board is also equipped with a CPU benchmark software under its own system. We can simply test it.
CPU benchmark test
Looking at the figure above, I believe that users who do not know much about stm32f426zit6u microcontroller are somewhat unknown. Therefore, the test result of 63481000 pixels / s only indicates the pixel filling rate? This seems to reflect the level of GPU and has little to do with CPU? Is there a mistake?
Obviously, ST will not make such low-level mistakes, nor will it be aimless. To explain this problem clearly, we need to go back to the introduction of St microcontroller above. One of the known important functions is the integration of LCD controller and St graphics dedicated chrome art accelerator, The chrome art accelerator can automatically handle the filling, copying and mixing of graphic elements, including pixel format conversion. Of course, as users, they urgently need real data, that is, compared with the case without chrome art accelerator, the graphics operation speed will be twice as fast, and the chrome art accelerator supports many third-party graphics stacks, such as through stemwin, St can provide a completely free graphic solution including wizard and user interface, and the lit screen at this time is the best proof. 63481000 pixels / s also reflects the image processing level of stm32f426zit6u microcontroller. Of course, it can't be compared with PC and follower, but compared with other MCU, it is arrogant enough.
In the hardware introduction of stm32f429i discovery development board, a special function is the integration of USB2.0 OTG. Here, we can also test it. First, you need to prepare a set of OTG cable of micro AB to USB host interface, insert the cable into the USB OTG port of the board, and insert the USB flash disk. You can see that the identification symbol of the USB flash disk appears next to the CPU occupancy. However, the program does not have an entrance to the USB flash disk to view the data inside, but if there are pictures in the USB flash disk, you can view them under the image browsing application, which is very good (see the figure below)
USB2.0 OTG function
It's a pity that no video file can be played. I'm really sorry that I can't demonstrate this. In addition, during many tests, I found that USB OTG sometimes can and sometimes can't be detected. The factory built-in system basically contains this content. Now we can download other routines to experience other features of stm32f429i discovery development board.
Stm32f429i discovery board supports several development tools, such as truestudio, IAR, KEIL, etc. engineers only need to select one suitable for themselves. The author only installed a keil on the computer, so basically all the board cards that can use this tool are taken as examples, and they are becoming a model of labor.
The information of Italian French semiconductor development board is very complete on the official website. I believe users who have used st board card know it clearly. The author doesn't like it much. The province is suspected of being branded with advertising. Download the information package provided by the official, which has corresponding routines. The three-axis gyroscope program introduced by the author before is also included. There is no more nonsense. Open source it, load routines, configure flash, compile and download.
Three axis gyroscope program code
This program code is much simpler than the three-axis gyro application demonstrated by jobs (guess). The screen only displays an arrow when the board
Our other product:
