preface
So far, I have also done 5 or 6 embedded projects, but in the past, I started from scratch, that is, I had no plan. If I wanted to do it there, I would implement it if I had an idea. This led to a lot of pitfalls and consumed me a lot of time. Of course, it's not bad, because I also got a good exercise and practice in it, but it's not applicable to doing it at work.
First of all, I would like to thank Huaqing Yuanjian for providing the teaching video of the security monitoring system project; It let me know how to complete a project in actual development from scratch. It helped me clarify the idea of project production, and also let me understand how important a good plan and agreement is for a project.
1, Personal perception
1. Design idea of layered system framework
When designing the embedded project, try to design and draw the layered system framework of the project before;
Most embedded projects involve multi platform and multi task development;
For this project, it involves
- The data communication between HTML and CGI is through boa server;
- Communication between A9 server and CGI;
- Communication between zigbee and A9;
- Work of the platform itself and mutual access between multiple platforms
Then it is necessary to design the whole project hierarchically, and divide each platform into one for separate processing (multi process and multi thread can be considered). When formulating communication protocols and selecting communication methods, different platforms can be connected with each other. When a project has problems, it can quickly locate which layer and which task has problems, which not only facilitates the division of labor and cooperation of most people.
Take the layered design of the project as an example:
2. Consideration of data flow
The ultimate goal of embedded design is to complete the correct data transmission. There are many transmission modes, such as Bluetooth, wifi, 3G/4G, serial port, etc;
Understanding the data flow of the project can help us correctly draw the software architecture, formulate reasonable communication contents and select appropriate communication methods.
Take this project as an example:
The data flow in this project is
- Uplink data: ZigBee – >a9 – > Web page (obtain environmental information)
- Downlink data: Web page – >a9 – >zigbee (issue command)
Communication mode:
- Upload data: ZigBee ---- > shared memory + semaphore upload data ----> display and give it to the user
- Data distribution: used to control hardware: ---- > message queue data distribution ----- > control hardware
3. Necessity of unified communication content
Communication content, that is, the communication structure contains the data content we want to transfer
In this way, the information in the whole project is transmitted in the same way, which is convenient for us to unify the communication of the whole thread or process
For example, in this project
data upload part:
Data type definition
typedef uint8_t unsigned char;
typedef uint16_t unsigned short;
typedef uint32_t unsigned int;
//Consider memory alignment
struct makeru_zigbee_info
{
uint8_t head[3]; //Identification bit:'m''s''m'makeru security monitor
uint8_t type; //Data type'z'---zigbee'a'---a9
------------->crc ...encryption algorithm <--------------
float temperature; //temperature
float humidity; //humidity
float light; //light intensity
float tempMIN; //Lower temperature limit
float tempMAX; //Upper temperature limit
float humidityMIN; //Lower humidity limit
float humidityMAX; //Upper humidity limit
float lightMIN; //Lower limit of light intensity
float lightMAX; //Upper limit of light intensity
uint32_t reserved[2]; //Reserved extension bits, 0 filled by default
//void *data; Kernel reserved extension interface reference version
};
struct makeru_a9_info
{
uint8_t head[3]; //Identification bit:'m''s''m'makeru security monitor
uint8_t type; //Data type'z'---zigbee'a'---a9
uint32_t adc; //adc voltage
uint32_t reserved[2]; //Reserved extension bits, 0 filled by default
//void *data; Kernel reserved extension interface reference version
};
struct makeru_env_data
{
struct makeru_a9_info a9_info; //a9 uploading data
struct makeru_zigbee_info zigbee_info; //zigbee uploading data
};
data distribution: (send data to the lower computer in the form of message queue)
//Message queue structure
#define QUEUE_MSG_LEN 32
struct msg
{
long type; //Message type used to judge when receiving messages from message queue
long msgtype;//Specific message type = = = device type
unsigned char text[QUEUE_MSG_LEN]; //Message body ====> CMD controls the specified device
};
long msgtype;//Specific message types
Assignment of message types:
1L: LED control
2L: Buzzer control
3L: Fan
4L: Setting of maximum temperature, humidity and light intensity
5L-6L-7L-8L,Extensions for individuals
9L: 3G communication module -GPRS
switch(msgbuf.msgtype){
case 1L: ... break;
....
default .... break;
}
A9-ZIGBEE General instructions
Command format: One byte, unsigned char Corresponding to the type of body in the message queue:
8 position
----------------------------------------
7 6 | 5 4 | 3 2 1 0
Platform No | Equipment No | Operating equipment
----------------------------------------
Platform No
0x00 00-0 number-ZigBee platform
0x40 01-1 number-A9 platform
0x80 10-2 number-STM32 platform(extend)
0xc0 11-3 number-retain(extend)
----------------------------------------
Equipment No Operation mask
0x00 LED 0x00 close all 0x40
0x01 Open all 0x41
0x02 Open LED2 0x42
0x03 Open LED3 0x43
0X04 Open LED4 0x44
0x05 Open LED5 0x45
0x06 closure LED2 0x46
0x07 closure LED3 0x47
0x08 closure LED4 0x48
0x09 closure LED5 0x49
----------------------------------------
0x10 buzzer 0x00 closure 0x50
0x01 Open 0x51
0x02 Auto alarm off 0 x52
0x03 Automatic alarm on 0 x53
----------------------------------------
0x20 Fan 0x00 Turn off the fan 0x20
0x01 Turn on the fan 0x21
----------------------------------------
0x30 extend
----------------------------------------
control command:
Platform number + Equipment number + Operation mask = command (Encapsulation of commands)
for example:
0x00 + 0x20 + 0x01 = 0x21 Fan on
0x40 + 0x10 + 0x01 = 0x51 Buzzer on
2, Summary of project knowledge points
1. HTML web page design and CGI
In the design of this project, html is used to draw web pages, CGI is used to process web page data, boa server is used to realize the communication between different languages, and form form is used to realize the communication between HTML and CGI; This is the development of user layer
2. Communication between HTML webpage and A9
send messages from web pages to A9, convert the data of web pages through CGI, and add the data to the message queue. Here we use the knowledge points of message queue, including the creation of message queue (msgget), receiving messages (msgrcv), sending messages (msgsnd);
refreshing data from A9 to web pages is achieved by sharing memory. CGI gets the data of shared memory and sends it to web pages Here we use the knowledge points of shared memory, including the creation of shared memory (shmget), mapping (shmat), and unmapping (shmdt); At the same time, semaphores should be added to synchronize critical resources;
3, the design idea of multithreading
A9 platform is the core platform of the project. It uses multithreading to process and run multiple tasks separately, and uses mutually exclusive locks, semaphores, and conditional variables to complete the synchronization and mutual exclusion between threads
the A9 platform controls the ZigBee coordinator downward through the serial port and interacts with the PC web page upward through the network cable, which requires separate threads for processing
4,zigbee environment acquisition
environmental acquisition needs to consider the content of acquisition, and then select the corresponding sensor to digitize the environmental information to be collected. This requires knowing the relevant knowledge of MCU development and reading the chip manual; And understand the usage of the sensor and the method of data processing; And master the principle of ZigBee wireless transmission
There may be a lot more to say, but the blogger's knowledge is limited and he can't say it comprehensively. Here is just a summary of my summary and perception from my project to the present I think the most important thing is to participate in the project production more and practice more. Only in this way can we have our own experience in the project production process. Thank you for seeing here
