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What is hardware testing?

Definition: Hardware testing is a process activity that checks for errors in the product hardware (structure, PCBA, key components, etc.) during the project development process to ensure its quality. Hardware testing is just one of the ways to control the quality of hardware products, and quality management includes a quality objective PPM+trilogy (quality planning quality control quality improvement).

The 7 main types of hardware product testing:

Signal quality testing - timing testing - functional testing - performance testing - fault tolerance testing - long-term testing - consistency testing - signal quality testing

Hardware testing steps and process:

Hardware testing before power on

1. Is the connection correct. Checking the schematic is crucial, and the first focus of inspection is whether the labeling of the chip's power supply and network nodes is correct, while also paying attention to whether there is any overlap in the network nodes. Another key point is the packaging of the original components, the packaging model, and the pin sequence of the packaging; Do not use top view packaging, remember! Especially for non pin packaging. Check if the connections are correct, including incorrect, missing, and multiple connections.

Hardware schematic design should adhere to some basic principles, which should be implemented throughout the entire design process. Although these principles are also reflected in successful reference designs, we still need to design and review our schematics based on these principles at all times, as we may have pieced them together. These principles include

a) Separation of digital power supply and analog power supply;

b) Digital ground and analog ground are separated, with single point grounding. The digital ground can be directly connected to the chassis ground (earth), and the chassis must be grounded;

c) Ensure that the resources of each module in the system do not conflict, for example, device addresses on the same I2C bus cannot be the same, etc;

d) Read the manuals of all chips in the system (usually design reference manuals) to see if their unused input pins need external processing. If necessary, corresponding processing must be done, otherwise it may cause internal oscillation of the chip, resulting in the chip not working properly;

e) Try to ensure software development convenience without increasing hardware design difficulty, or exchange lower hardware design difficulty for more convenient, reliable, and efficient software design. This requires hardware designers to understand the underlying software development and debugging, which requires higher requirements;

f) Power consumption issue;

g) The problem of product heat dissipation can be addressed by adding heat sinks or fans to chips with high power consumption and heat generation. The product chassis should also consider this issue and cannot be made into a thermal insulation box, as circuit boards are harmful to the "greenhouse"; We also need to consider the placement of the product, preferably in a location with a large space and smooth air flow, which is conducive to heat dissipation.

Tracing back to the source, check whether the schematic design is correct according to the principles of schematic design.

There are usually two methods for checking lines:

1) Check the installed circuits according to the circuit diagram, and inspect the installed circuits one by one in a certain order based on the circuit connections;

2) Refer to the actual circuit diagram and check the wiring around the components. Check the wiring of each component pin once and verify if it exists on the circuit diagram. To prevent errors, wires that have already been checked should usually be marked on the circuit diagram. It is best to use a buzzer with an ohm range pointer multimeter to test and directly measure the pins of the components. This can simultaneously detect areas of poor or incorrect wiring;

2. Is there a short circuit in the power supply. Before debugging, do not turn on the power. Use a multimeter to measure the input impedance of the power supply. This is a necessary step! If the power supply is short circuited, it can cause the power supply to burn out or have more serious consequences. When it comes to the power supply, a 0 ohm resistor can be used as a debugging method. Attention: Do not solder the resistor before powering on. Check that the voltage of the power supply is normal before soldering the resistor onto the PCB to supply power to the subsequent units, in order to avoid burning out the chips of the subsequent units due to abnormal voltage of the power supply. Add protective circuits in circuit design, such as using recovery fuses and other components;

3. Installation status of electronic components. The main purpose is to check the polarity of components such as light-emitting diodes, electrolytic capacitors, rectifier diodes, and whether the pins of transistors correspond. For transistors, the pin order of devices from different manufacturers with the same function is also different. It is best to use a multimeter to test it;

Perform open circuit and short circuit tests first to ensure that there will be no short circuit phenomenon after power on. If the testing points are set up properly, it can achieve twice the result with half the effort. The use of 0 ohm resistors is sometimes beneficial for high-speed circuit testing; After completing the hardware testing before power on, the next step of operation - power on testing can be started.

Power on detection

1. Power on observation: After power on, do not rush to measure electrical indicators, but observe whether there are any abnormal phenomena in the circuit, such as smoking, abnormal odors, touching the outer packaging of the integrated circuit with your hand, and whether it is hot. If any abnormal phenomenon occurs, the power should be immediately turned off and the fault should be resolved before turning it back on.

2. Static debugging: Static debugging generally refers to DC testing conducted without adding input signals or only adding fixed level signals. A multimeter can be used to measure the potential of each point in the circuit. By comparing it with theoretical estimates and analyzing the circuit principles, the DC working state of the circuit can be determined to be normal, and damaged or critical components in the circuit can be detected in a timely manner. By replacing components or adjusting circuit parameters, the DC working state of the circuit can meet the design requirements.

3. Dynamic debugging: Dynamic debugging is carried out on the basis of static debugging. Suitable signals are added to the input of the circuit, and the output signals of each test point are sequentially detected according to the direction of the signals. If any abnormal phenomenon is found, the cause should be analyzed and the fault should be eliminated before debugging until the requirements are met.

During the testing process, one should not rely solely on intuition, but always rely on instruments for observation. When using an oscilloscope, it is best to set the signal input mode to "DC" mode. Through DC coupling, the AC and DC components of the measured signal can be observed simultaneously. Through debugging, finally check whether the various indicators of the functional block and the whole machine (such as signal amplitude, waveform shape, phase relationship, gain, input impedance, and output impedance, etc.) meet the design requirements. If necessary, further propose reasonable modifications to the circuit parameters.