Abstract：Embedded hardware design is a systematic work. For engineers, understanding the processes and general methods involved is significant for carrying out their work. Today, we will briefly discuss the general processes in hardware design.
1. Requirement Analysis
Requirement Analysis involves conducting requirement analysis with clients and determining the final requirements, establishing product technical plans, system block diagrams, and other guiding documents. Special attention should be paid to the following two points:
First, the product plan design reflects the true needs of users and has a certain market foresight, with the same series of products having inheritance and scalability, considering partial compatibility with other series products;
Second, the product technical plan is crucial for the success or failure of a product. Spending more time considering the product technical plan upfront can save more time later on troubleshooting product bugs, such as the choice of communication method, whether to use CAN or 485, etc.
2. Hardware Schematic Design
Hardware Schematic Design involves selecting key components and communicating with suppliers. The circuit should consider derating design, outputting schematic design documents, schematic output review, and soft/hardware interface document output.
Key components refer to the selection of the MCU and primary/secondary power sources, whether domestic or foreign brands, whether they are stable mass production products, if the delivery time meets requirements, if they are common materials, whether there are other pin-to-pin substitutes available on the market, and the schematic review requires a thorough examination of the circuit, with particular attention to new circuit parts, conducting preliminary simulations, and building circuits for verification if conditions allow.
The soft/hardware interface document can generally be output to the driver engineer after the schematic is finalized, as the driver engineer can conduct relevant work during the PCB layout, prototyping, and assembly stages without delaying the project timeline, allowing the driver to complete basic tasks once the prototype returns.
3. PCB Design and System Stacking
PCB Design and System Stacking involve outputting to PCB layout engineers for pre-layout after the schematic is finalized. This process generally requires repeated iterations, constant compromises, and optimizing a reasonable layout. After pre-layout is completed, a 3D model is output to the structural engineer to check for interferences, and adjustments are made to finalize the system stacking scheme. Important points to note in PCB design include:
First, focus on layout; a smooth layout makes subsequent work easier, requiring PCB layout engineers to have a deep understanding of the circuit;
Second, power layout routing; many product issues stem from power problems, requiring special attention. The schematic design and PCB layout routing design must consider safety regulations and necessary certifications;
Third, handling critical signals, including clock, high-speed, differential, analog, reset, and other sensitive signals, ensuring proper isolation between signals.
4. Prototype Production
Prototype Production involves assembling the prototype after the PCB is completed, which generally requires hardware engineers to follow up, including outputting the BOM, organizing the assembly files (by PCB engineers), communicating issues during the assembly process with the factory, and confirming the first article.
5. Prototype Debugging
Prototype Debugging generally involves the following steps:
First, after the prototype returns, conduct a PCBA appearance inspection for issues like poor soldering, short circuits, polarity device soldering errors, component soldering faults, and obvious soldering mistakes;
Second, before powering on, use a multimeter to measure the power output for short circuit phenomena, generally checking the short circuit conditions of each power supply to ground;
Third, measure system voltages with a multimeter to ensure they are within the designed range, such as system 5V, 3.3V, 2.8V, 1.2V, etc., and conduct power-on tests for each level of power supply using an oscilloscope to ensure there are no significant steps, ringing, or overshoot issues;
Fourth, test the crystal oscillator to see if the system crystal oscillator powers on and oscillates, such as 24MHz, 32.768KHz;
Fifth, test the reset circuit; for hardware watchdog circuits, check the WDG_WDI and RESET signal waveforms and device operating states under feeding conditions, and whether the WDG_WDI and RESET signals meet the timing specifications in the datasheet when not fed;
Sixth, conduct a lighting test (to check if the system operates normally, which can also be done by outputting its working state via serial port);
Seventh, specific hardware debugging items depend on the project, and many other issues may arise during hardware debugging, such as abnormal power cycling, 4G ping network issues, screen glitches, speaker distortion, and SD card communication anomalies.
6. Prototype Debugging
Prototype Debugging generally involves the following steps:
First, after the prototype returns, conduct a PCBA appearance inspection for issues like poor soldering, short circuits, polarity device soldering errors, component soldering faults, and obvious soldering mistakes;
Second, before powering on, use a multimeter to measure the power output for short circuit phenomena, generally checking the short circuit conditions of each power supply to ground.