Analysis of Graphical Programming Methods for Single Chip Microcomputers

Single-chip microcomputers can be programmed in assembly language, high-level languages ​​C and Basic, or graphical languages. Programmable controllers are widely used in industrial control. The microcontrollers in their CPU modules are often ordinary single-chip microcomputers, while programmable controllers can be programmed in ladder diagrams or flowcharts. The current intelligent educational robot controllers all use single-chip microcomputers, and most of these robots support flowchart programming. The Ability Storm series robots of Shanghai Guangmaoda Electronic Information Co., Ltd. use VJC visual flowcharts and C language programming; the Zhongming robot series uses Robot Express software programming, which is also a visual flowchart and C language programming; the Lego series of Simia, Bosiweilong robots, the VEX series robots of the United States, and the robot DIY series of Ssangyong can all be programmed in visual flowcharts and C language. The core of the control system of these robots is a single-chip microcomputer. It can be seen from this that the development of ordinary single-chip microcomputers can definitely use flowchart programming. In fact, the flowchart compilation software of the robot can be used as the programming software of the corresponding single-chip microcomputer in turn. The following example uses a detailed explanation of how to use graphical programming for single-chip microcomputers.

1 Problem Description

On a certain machine, two motors drive the workbench to move sequentially through ball screws, as shown in Figure 1. The two motors are controlled by a single-chip microcomputer system to achieve the specified sequential action. When the travel switch KX1 is pressed, motor D1 drives the clamping mechanism to move right. When it moves right to the impact block pressing KX2, motor D1 stops, and this state is delayed for a period of time T1. Motor D2 starts to move in the following order: when the travel switch KX3 is pressed, motor D2 drives the workbench to move right. When the workbench moves right to the impact block pressing KX4, motor D2 stops, and this state is delayed for a period of time T2; then motor D2 reverses and drives the workbench back to the left. When the workbench returns to the left and presses KX3, motor D2 stops, and motor D1 reverses at the same time, loosens the clamping mechanism until KX1 is pressed, and motor D1 stops.

Figure 1 Sequential actions of the clamping mechanism and the workbench

The sequence is shown in Figure 2.

Figure 2 Action sequence diagram

2. Composition of single chip microcomputer control system

There are many schemes to realize the above control functions, such as relay contactor control system, programmable controller control system, single-chip microcomputer control system, etc. This paper uses single-chip microcomputer control system to realize the above control action. The composition of single-chip microcomputer control system is shown in Figure 3.

Figure 3 MCU control system structure diagram

The single-chip microcomputer uses the MC68HC11E1 of Motorola. In order to meet the needs of the simulation experiment, the single-chip microcomputer control system uses the main control board of the Ability Storm robot ASUII of Shanghai Guangmaoda Electronic Information Co., Ltd. The travel switches KX1~KX4 are simulated by the collision switches on the robot, and the collision switch circuit is shown in Figure 4(a). The motors D1 and D2 are simulated by the driving motors of the two wheels of the robot, and the circuit is shown in Figure 4(b). Among them, the motor drive chip selected is SN754410 of TI.

Figure 4. Collision switch circuit and drive motor circuit on the AbilityStorm robot

3 VJC Procedure Flow

Use the programming development environment VJC1.6 of the Ability Storm robot (which can be downloaded from the website of Shanghai Grandar Electronic Information Co., Ltd. www.grandar.com ) to compile, debug and download the program. For the above-mentioned single-chip dual-motor start-stop control system, the flowchart compiled by VJC1.6 is shown in Figure 5. For the actual single-chip control system, as long as the corresponding sensors and their drive circuits, motors and their drive circuits are changed to components that adapt to the actual object, this single-chip control board and corresponding programming software can still be used. Further applications can expand the software and hardware system.

The overall program is a cyclic program. In each cycle, the four collision switches are detected in turn, and the motor is started or stopped according to the motor's action sequence. The use of program modules and the setting of variables are omitted here. Please refer to the manual or contact Shanghai Guangmaoda Electronic Information Co., Ltd.

The flowchart of FIG5 can be converted into a C language program in the VJC1.6 environment. For details, please refer to the use of VJC1.6.

Programs compiled in the VJC1.6 environment, whether flowcharts or C language programs, can be directly downloaded to the flash memory or EEPROM of the microcontroller, which is why this programming and development method is popular. However, this method is currently only used in the program development of intelligent robots with microcontrollers as the core. There is no such graphical programming environment specifically for microcontroller development. I believe that this method will appear in the near future.

Figure 5 Dual motor start-stop control flow chart

Conclusion

The functions realized by the single-chip microcomputer system here are equivalent to a programmable controller system, and the programming language is a flowchart language. It can be seen that some single-chip microcomputer systems can be slightly expanded to become a fully functional programmable controller that can use flowchart programming, C language programming and assembly language programming, thus keeping pace with existing programmable controllers in the field of industrial control.