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[ESP32] Investigation of the cause of cracked speaker sound and no playback due to wiring error (magnifying glass and oscilloscope)

When the IC package of the Class D amplifier was changed from TQFN to WLP, 4 out of 25 were defective in the speaker area as follows. Investigate the cause of sound crackling and audio not being played back. Verify if the sound crackling is resolved by first lowering the volume in the application. Next, using a magnifying glass, visually check for wiring defects.

2024.09.05 2026.04.16

Development/DesignEntrepreneurMiabuilt-in(C++)electronic circuit

[ESP32] From development board to designing your own printed circuit board and making it into a product

The cat-shaped talking robot Mia is developed on a home-made board using an ESP32 Wi-Fi Bluetooth module; this memorandum summarises the process from the initial development using an ESP32 development board to the creation of a home-made board and several changes for the product.

2024.04.28 2026.04.11

Development/Designelectronic circuit

[ESP32 custom board] Result of investigating the cause of board defects by measuring voltage with an oscilloscope.

When wiring voltage is to be measured, the wiring on the board is often covered with resist (insulation layer), so voltage cannot be measured by applying a probe over the wiring as it is, so lightly scratch the area to be measured with a cutter to expose the copper foil part before measuring the voltage.

Development/Designelectronic circuit

[ESP32] Modified circuit with power supply noise countermeasures to avoid surface mounting errors.

The MAX98357 itself needs to be connected to pins 25, 26 and 22 of the ESP32 WROOM 32E. keep the I2S signals (BCLK, LRCLK and DIN) as close as possible to pins 25 and 26 of the ESP32, as keeping the wires short reduces the risk of signal degradation and cross-talk. Attempt to optimise decoupling capacitors in the circuitry around the power supply to reduce power supply noise.

Development/DesignEntrepreneurMiabuilt-in(C++)electronic circuit

[Stock issue] What if a part is out of stock when I place my order? Using JLCPCB’s pre-order.

In order to deal with out-of-stock issues like this one when they decide to order, JLCPCB allows pre-ordering, which means that the parts can be ordered before the PCB assembly is ordered and kept in stock at JLCPCB until the PCBA service is required. These pre-ordered parts are sent together with the PCB (and surface mount if you have also asked for surface mount), rather than separately from the PCB and only the parts are sent to you.

Development/DesignEntrepreneurMiaelectronic circuit

Create PCB by EasyEDA and order PCB by JLCPCB. If you want to keep costs down, request 2 boards to be mounted.

Create schematics in EasyEDA and convert the schematics to PCBs Work on the PCBs includes component placement, number printing, board outline drawing, wiring with auto routing, creating mounting holes and creating solid copper foil After completing the work on the PCBs, order the boards from JLCPCB.

2023.09.17 2024.06.30

Development/Design

[Electronic Circuit] Found defective products after 100 boards were installed and filed a Quality Complaint with JLCPCB.

The order was placed with JLCPCB for 100 boards, but in reality some of the pin headers were slightly out of level, resulting in LCD displays interfering with each other and not fitting together The JLCPCB order history section has a 'Quality Complaint' field where you can enter the nature of the fault and the number of faulty boards. and the number of defective boards.

2024.05.24 2024.06.08

Development/Designelectronic circuit

[JLCPCB] I received a confirmation email after ordering 100 boards. PCB operation is not checked

If there is no problem with the PCB layout, you will not receive an email from JLCPCB, so if you receive an email, it is when there is a problem, such as an incomplete circuit. Also, JLCPCB does not check the functionality of your own PCB, so you need to look at the schematic and PCB yourself to determine if the order is correct.

2024.05.08 2024.06.06

Development/Designelectronic circuit

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