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Difference between PDM microphones and I2S: Why does PDM require a decimation filter?

A PDM microphone is a digital microphone that expresses audio signals as a density of pulses. The converted signal consists of “high-density ones and zeros” and includes high-frequency components that exceed the human audible range (20 Hz to 20 kHz). On the other hand, I2S microphones transmit voice data in PCM format

Development/Designelectronic 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 2024.11.09

Development/Designelectronic circuit

Servo motor vs. DC motor: sound comparison

The sound volume was compared between a servo motor and a DC motor as a mechanism to move the mouth of a talking robot.The DC motor was connected to an ESP32 using an L293D motor driver, and the gears to be attached were made using a 3D printer. The rack and pinion moves by itself, but not when a rubber is attached.

2023.08.28 2024.10.26

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.

built-in(C++)Development/Designelectronic circuitEntrepreneurMia

[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.

built-in(C++)Development/Designelectronic circuitEntrepreneurMia

[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/Designelectronic circuitEntrepreneurMia

[MAX98357A] Changed IC package of class D amplifier from TQFN to WLP

The MAX98357A series of ClassD audio amplifiers is available in TQFN and WLP packages.The WLP package is smaller and more cost-effective than the conventional TQFN package, as it does not require expensive through-hole vias (connection pins that pass through the PCB).

2023.12.28 2024.08.21

Development/Designelectronic circuit

[ESP32] Understanding the automatic boot loader mechanism and truth table

The automatic bootloader of the ESP32 is a function that enables automatic programme writing when the PC instructs the programmer to write the programme (by pressing the Upload button on PlatformIO) without having to manually press the EN or BOOT (IO0) pins.

2023.08.13 2024.08.02

Development/Designelectronic circuit

[Speaker] I attended the workshop on acrylic speaker amplifiers. I learned a lot.

I decided to start a speaker business for the hearing impaired in January this year, so this workshop came at the right time when I wanted to deepen my understanding around speakers.

2023.01.28 2024.08.01

Development/Designelectronic circuit

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