Online burning, which integrates burning and testing, has attracted more and more people's attention. In order to speed up the efficiency of programming, programming tools or fixtures are often made, and a relatively long wiring is required between the tooling, fixture and the programmer. The longer the wiring, the faster the signal attenuation, and the poor programming rate will also increase.
Figure 1 Online programming fixture
1. Increase the shielding layer to prevent electromagnetic interference and electrostatic interference
As a tool that communicates closely with the chip, the programmer is more sensitive to electromagnetic interference. The burning environment is generally a factory workshop. High-power equipment makes electromagnetic interference more serious. In order to reduce electromagnetic interference, we can add a shielding net to the burning line, or choose shielding function lines, such as shielded cables, network cables, etc. It is best to wear electrostatic gloves during operation to prevent electrostatic interference.
2. Choose a wire with strong conductivity
The integrity of signal transmission is related to the material, length and thickness of the wire. You can choose a thicker and more conductive wire. A good material can reduce internal resistance and reduce signal loss, such as pure copper wire, gold-plated wire, and silver-plated wire Line etc.
Figure 2 Metal resistivity
Third, reduce the communication frequency
Communication frequency is an important parameter for information transmission. The higher the frequency, the faster the transmission speed, but the attenuation of the signal will increase with the increase in frequency, and will rapidly weaken as the transmission distance increases. Therefore, when the wiring is longer, it can be appropriate Reduce the communication frequency to increase the stability of communication.
Fourth, connect a pull-up or pull-down resistor on the key signal line
The programming interface of some chips has relatively weak drive capability. It is necessary to add appropriate pull-up or pull-down resistors to the interface to enhance the drive capability. For example, IIC and SWIM interfaces need to connect a strong pull-up resistor to the data line, and the car key chip PCF79xx , NCF29xx, etc. need to connect a pull-down resistor on the clock line, etc.
5. Choose a programmer with strong driving ability
The driving ability of the programmer pins will directly affect the length of the wiring. Some programmers on the market that support online directly lead to the IO port of the internal control chip or the pins of the FPGA as the input and output of the programming signal. Their driving ability is better. Weak, when the user's wiring is relatively long (generally greater than 30cm), signal distortion will occur, resulting in unstable programming. When choosing the programmer, you need to choose a professional online programmer, such as the P800isp programmer of Zhiyuan Electronics. Through the multi-channel signal enhancement processing, the driving ability of the programmer is increased, and a series of problems of too long wiring are solved.
Figure 3 Waveform comparison between P800isp and some programmers
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