Engage in embedded design, to understand development needs and environment

The characteristics of the microcontroller:

(1) Due to the limitation of integration, the on-chip memory capacity is small, generally ROM: 8KB or less;

(2) Internal RAM: 256KB or less.
(3) High reliability
(4) Easy to expand
(5) Strong control function
(6) Easy to develop

ARM features:

(1) Comes with inexpensive program memory (FLASH) and non-volatile data memory (EEPROM). These memories can be erased multiple times, making program development experiments more convenient and more reliable.

(2) High speed and low power consumption. Under the same crystal oscillator condition as M51 MCU, the working speed of AVR MCU is 30-40 times that of M51 MCU; and the sleep function and CMOS technology are added, so that its power consumption is much lower than that of M51 MCU.

(3) Industrial grade products. With high current output, it can directly drive SSR and relay, and has a watchdog timer to prevent the program from flying, thus improving the anti-interference ability of the product.

(4) Super-function reduced instructions with 32 general-purpose working registers, equivalent to 32 accumulators in the M51 microcontroller! Thereby overcoming the bottleneck effect of the operation of a single accumulator.

(5) The program is easy to download. AVR microcontrollers can be downloaded in parallel or serially, without the need for expensive programmers. In addition, you can also download it online! In other words, program modification and programming can be performed directly on the board.

(6) With analog comparator, pulse width modulator, analog to digital conversion function. It makes analog signal processing in industrial control easier and more convenient.

(7) The functions of important resources inside the microcontroller such as parallel port, timer counter and interrupt system have been greatly improved, making it more suitable for real-time control of industrial production processes.

(8) Its clock frequency can be externally connected or can be used with the internal oscillator of the microcontroller. Its frequency can be set from 1MHz to 8MHz, which makes the hardware development and production more compact.

(9) Powerful communication function, built-in synchronous serial interface SPI, universal serial interface UAST, two-wire serial bus interface TWI (I2C), making network control and data transmission more convenient.

(10) Super security feature, the application can use multiple protection locks. It can quickly complete the commercialization of manufacturers' products at low prices. In addition to the above features, "zero peripherals" is also an important feature of AVR embedded microcontrollers. Because the chip has built-in program memory, crystal oscillator and added online assembly function.

Therefore, the AVR microcontroller chip is connected to the DC power supply, and a program can be downloaded to work independently. No additional external equipment is required, no expensive programmers and simulation devices are required. This brings convenience to our learning and development.

FPGA features:

(1) Using FPGA to design ASIC circuit (application specific integrated circuit), users can obtain a shared chip without casting production.

(2) The FPGA can be used as a mid-sample for other fully custom or semi-custom ASIC circuits.

(3) There are a lot of flip-flops and I/O pins inside the FPGA.

(4) FPGA is one of the devices with the shortest design cycle, the lowest development cost and the lowest risk in ASIC circuits.

(5) FPGA adopts high-speed CMOS technology, low power consumption, and can be compatible with CMOS and TTL levels.

It can be said that the FPGA chip is one of the best choices for improving the system integration and reliability of small batch systems.

The FPGA is set up by the program stored in the on-chip RAM, so the on-chip RAM needs to be programmed during operation. Users can use different programming methods according to different configuration modes.

When power is applied, the FPGA chip reads the data in the EPROM into the on-chip programming RAM. After the configuration is completed, the FPGA enters the working state. After the power is turned off, the FPGA is restored to a white chip, and the internal logic relationship disappears. Therefore, the FPGA can be used repeatedly. The FPGA programming does not require a dedicated FPGA programmer, just a general EPROM, PROM programmer. When you need to modify the FPGA function, you only need to change one EPROM. In this way, the same FPGA, different programming data, can produce different circuit functions. Therefore, the use of FPGAs is very flexible.

Embedded system features

1, the system kernel is small

Since embedded systems are generally used in small electronic devices, the system resources are relatively limited, so the kernel is much smaller than the traditional operating system. For example, Enea's OSE distributed system, the kernel is only 5K, and the kernel of Windows? There is simply no comparability.

2, strong specificity

The embedded system is very personalized, and the combination of software system and hardware is very close. Generally, the system is transplanted for hardware. Even in the same brand and the same series of products, it is necessary to change and increase according to the system hardware. to modify. At the same time, for different tasks, it is often necessary to make major changes to the system. The compilation and download of the program should be combined with the system. This modification and the "upgrade" of the general software are two concepts.

3, system streamlined embedded system generally does not have a clear distinction between system software and application software, does not require its function design and implementation is too complicated, which on the one hand is conducive to control system cost, but also conducive to system security.

4. High real-time system software (OS) is the basic requirement of embedded software. And software requires solid-state storage to increase speed; software code requires high quality and high reliability.

5, embedded software development to standardize, you must use a multi-tasking operating system

Embedded system applications can run directly on the chip without an operating system; however, in order to properly schedule multitasking, utilize system resources, system functions, and expert library function interfaces, users must choose RTOS (Real-Time Operating System). Development platform, in order to ensure the real-time performance, reliability, and reduce development time to ensure software quality.

6. Embedded system development requires development tools and environments.

Because it does not have the bootstrapping development capability itself, even if the user can't modify the program functions after the design is completed, there must be a set of development tools and environments to develop. These tools and environments are generally based on soft software. Hardware devices and various logic analyzers, mixed signal oscilloscopes, etc. At the time of development, there are often concepts of host and target machines. The host is used for program development, and the target machine is used as the final execution machine.