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CW training aid

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Hardware design

This section contains circuit schematics, PCB design and components.

ESP32

This ESP32 is at the heart of the circuit board. The basic surface mount processor requires several support circuits for power up, reset and programming via a usb socket. This external ESP32 circuitry is based on the application data sheets from the manufacturer's website: espressif.com

I have added an external power supply which is only needed if USB power is not sufficient and link P2 allows the appropriate input power to be selected. The buck converter (U4) can be omitted if the device is only to be powered from the USB connector.

I found the auto program mode reset to be unreliable and added link U12 to allow this to be disabled. Program mode can still be selected by pressing switch SW2 on start up or the main control button on the device which uses the same i/o port.

ESP32 dev board USB connector circuit schematic

Schematic for the ESP32 programming enable circuit

Schematic for the ESP32 programme and reset buttons

Schematic Ircuit diagram for the power section of the ESP32 CW trainer

12V input to 5V converter, external/usb source selection link and 3.3V regulator

Reset and program buttons

Auto program mode reset

ESP 32 connections

USB power/data connector

Serial communication UART

Audio input and output

The audio input circuits cater for direct connection using a 3.5mm plug/socket or for a microphone. If one type of input is not required then the relevant components need not be fitted.

The audio output circuitry also caters for direct output as well as a built in speaker. If the speaker is not required then the relevant components can be omitted.

Schematic for ESP CW trainer audio input circuitry

Schematic for ESP CW trainer microphone circuit

Schematic for ESP CW trainer audio output circuitry

Direct audio input conditioning and amplifier

I2S MEMS microphone

Direct audio out connector, amplifier and internal speaker

External connections

TFT, CW key/paddle, rotary encoder, button and optional gyroscope. The gyroscope is not needed for the CW trainer and doesn't need to be fitted. Link P1 is required and needs to be connected in the "key" position for the CW key or paddle to work.