Abstract:
Embedded hardware design is a systematic task. For engineers, understanding the processes and general methods involved is significant for carrying out their work. Today, let’s briefly discuss the general process in hardware design.
1. Requirement Analysis
Requirement Analysis involves working with clients to analyze requirements and determine the final needs, establishing guiding documents such as product technical solutions and system block diagrams. Special attention should be given to the following two points:
First, the product solution design should reflect the true needs of users and possess a certain market foresight. Similar products should have inheritability and scalability, considering partial compatibility with other series products;
Second, the quality of the product technical solution is crucial to the success or failure of a product. Spending more time considering the product technical solution at the beginning can save more time later on resolving product bugs, such as choosing communication methods, whether to use CAN or 485, etc.
2. Hardware Schematic Design
Hardware Schematic Design involves selecting key components and communicating with suppliers. The circuit design should consider derating design, output of schematic design documents, schematic output review, and output of hardware-software interface documents. Key components refer to the selection of MCUs and primary and secondary power supplies, whether to use domestic or foreign brands, whether they are stable products for mass production, whether the delivery time meets requirements, and whether they are common materials available on the market. There should be pin-to-pin alternative materials available. The schematic review requires a detailed examination of the circuit, with a focus on new circuit parts. It is advisable to conduct preliminary simulations and, if conditions allow, build the circuit for verification. The hardware-software interface document can generally be output to the driver engineers after the schematic is finalized, as the driver engineers can work on related tasks during the PCB layout, prototyping, and assembly phases without delaying the project timeline. The basic prototype can be returned with the driver mostly completed.
3. PCB Design and System Stacking
PCB Design and System Stacking occurs after the schematic is finalized, and we output to PCB layout engineers for pre-layout. This process generally requires repeated iterations, constant compromises, and optimization to achieve a reasonable layout. Once the pre-layout is completed, a 3D model is output to structural engineers to check for interferences, and adjustments are made to finalize the system stacking plan. A few points to note in PCB design include:
First, focus on layout; a smooth layout simplifies subsequent work. The PCB layout engineer must have a deep understanding of the circuit;
Second, power layout and routing; many product issues arise from power problems, so it is essential to focus on this. The schematic design and PCB layout must consider safety regulations and required certifications;
Third, handling of key 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 PCB after the board is completed, generally requiring hardware engineers to oversee the process, including BOM output, organization of assembly files (by PCB engineers), communication of issues during the factory assembly process, and confirmation of the first piece.
5. Prototype Debugging
Prototype Debugging typically involves the following steps:
First, after the prototype returns, conduct a PCBA appearance inspection for issues such as poor soldering, solder shorts, incorrect polarity device soldering, component soldering omissions, or obvious soldering errors;
Second, before powering on, use a multimeter to check for short circuits in the power output, typically checking for shorts to ground across various power supplies;
Third, measure system voltages using a multimeter to ensure each voltage is within the designed range, such as system 5V, system 3.3V, system 2.8V, system 1.2V, etc., and then use an oscilloscope to test the power on and off for each level to ensure there are no significant steps, ringing, overshoot, or other issues;
Fourth, crystal oscillator testing to check if the system oscillator powers on and oscillates, such as 24MHz, 32.768KHz;
Fifth, testing the reset circuit; if there is a hardware watchdog circuit, test the WDG_WDI and RESET signal waveforms under feeding conditions and device operating status, and check if the WDG_WDI and RESET signals meet the timing specifications in the datasheet when feeding is stopped;
Sixth, LED test (to check if the system operates normally, can also output its working status via serial port)
Seventh, specific hardware debugging items will depend on the specific project. Many other issues may arise during hardware debugging, such as abnormal power on/off, 4G ping network issues, screen artifacts, speaker distortion, SD card communication issues, etc.
6. Prototype Debugging
Prototype Debugging typically involves the following steps:
First, after the prototype returns, conduct a PCBA appearance inspection for issues such as poor soldering, solder shorts, incorrect polarity device soldering, component soldering omissions, or obvious soldering errors;
Second, before powering on, use a multimeter to check for short circuits in the power output, typically checking for shorts to ground across various power supplies;
Author: Brain, Source: 8th Line Engineer
Disclaimer: This article is reproduced with permission from the “8th Line Engineer” public account. The reproduction is for learning and reference only and does not represent the views of this account. This account does not bear any infringement responsibility for its content, text, or images.
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