1, in the layout of components, the relevant components should be put as close as possible, for example, the clock generator, crystal oscillator, CPU clock input end are easy to produce noise, and should be close to them when they are placed. For those devices which are easy to produce noise, small current circuits, and large current circuit switching circuits, we should try to make it far away from the logic control circuit and storage circuit (ROM, RAM) of the single chip microcomputer. If possible, these circuits can be made into the circuit board, which is beneficial to anti-interference and improve the reliability of the circuit work.

2, try to install decoupling capacitors next to chips such as ROM and RAM as far as possible. In fact, the wiring, wiring and wiring of printed circuit boards may have large inductance effect. Large inductors may cause severe switching noise spikes on the Vcc line. The only way to prevent Vcc from switching to the peak of noise on line is to place an 0.1uF electronic decoupling capacitor between the VCC and the power source. If the surface mount element is used on the circuit board, the chip capacitor can be directly attached to the element and fixed on the Vcc pin.

3. In the single chip computer control system, there are many kinds of ground lines, such as systematic, shielding, logical, simulation, and so on. The layout of the ground line is reasonable, which will determine the anti-interference ability of the circuit board. When designing the ground and grounding points, the following problems should be considered:

(1) logic and simulation must be separately cabled, and they can not be used together, and their respective ground wires are respectively connected to the corresponding power ground wires. When designing, the analog ground wire should be thickened as much as possible, and the grounding area of the lead terminal should be increased as much as possible. Generally speaking, the analog signals between input and output are preferably isolated by the optocoupler.

(2) the ground line should be as coarse as possible. If the ground line is very thin, the ground wire resistance will be larger, which causes the change of the grounding potential as the current changes, resulting in the instability of the signal level, which leads to the decrease of the anti-interference ability of the circuit. If the wiring space is allowed, to ensure that the width of the main ground wire is at least 2~3mm, the grounding line on the component pin should be about 1.5mm.

(3) pay attention to the choice of the location. When the frequency of the signal on the circuit board is lower than 1MHz, the influence of the electromagnetic induction between the wiring and the components is very small, and the circulation of the grounding circuit has a great influence on the interference, so it is necessary to adopt a bit of grounding, so that it does not form the loop. When the signal frequency on the circuit board is higher than 10MHz, the ground wire impedance becomes very large because of the obvious inductance effect of the wiring, and the circulation of the grounding circuit is no longer the main problem. Therefore, multi point grounding should be adopted to minimize ground impedance.