A few tips on hardware design: cost savings

Cost saving


phenomenon 1: It doesn't matter what value these pull-up / pull-down resistors have, just choose an integer of 5K . Comment: There is no 5K resistance value on the market . The closest one is 4.99K (accuracy 1% ), followed by 5.1K (accuracy 5% ), and their costs are 4 times and 2 times higher than 4.7K with an accuracy of 20% , respectively. The resistance values ​​of resistors with 20% accuracy are only 1 , 1.5 , 2.2 , 3.3 , 4.7 , and 6.8 (including integer multiples of 10 ); similarly, capacitors with 20% accuracy also have only the above values. If other values ​​are selected, higher accuracy must be used, and the cost will be multiplied several times, but it will not bring any benefits. Phenomenon 2: What color should be chosen for the indicator light on the panel? I think blue is more special, so let's choose it. Comment: Other colors such as red, green, yellow, orange, etc., regardless of size (



5MMThe following) packaging, has been mature for decades, the price is generally less than 50 cents, while the blue is something invented in the past three or four years, the technical maturity and supply stability are poor, but the price is four or five times more expensive. At present, the blue indicator light is only used in occasions that cannot be replaced by other colors, such as displaying video signals.

Phenomenon 3: This logic can be built with 74XX gate circuits, but it is too rustic, it is better to use CPLD , which looks more high-end .
Comment: The gate circuit of 74XX is only a few cents, while CPLD is at least dozens of yuan ( although GAL/PAL is only a few yuan, the company does not recommend it). Not only has the cost increased by N times, but it also adds several times of work to production, documentation and other work. Phenomenon 4: Our system requirements are so high that all chips including MEM , CPU , FPGA , etc. must be selected at the fastest . Comment: In a high-speed system, not every part works at a high speed, and the price will almost double for each level of device speed increase, and it will also bring great negative impact to signal integrity issues. Phenomenon 5: The PCB design requirements of this board are not high, so use thinner wires and automatically route. Comment: Automatic routing will inevitably occupy a larger PCB area and generate many times more vias than manual routing. In large-volume products, the factors that PCB manufacturers consider when reducing prices include line width and the number of vias, in addition to business factors. They affect the yield rate of PCB and the number of drill bits consumed, respectively, saving the supplier's cost and finding a reason for the price reduction. Phenomenon 6: As long as the program is stable, it is not the key that the code is longer and the efficiency is lower. Comment: The speed of the CPU and the space of the memory are bought with money. If you spend a few more days writing the code to improve the efficiency of the program, then the cost saved by reducing the CPU main frequency and reducing the memory capacity is definitely worthwhile. CPLD/FPGA design is similar.