Dead-bug BLE LED blinky

Description

WCH CH571K is an interesting BLE chip. It only needs two capacitors and one crystal to run. It will enter the bootloader on power-up, and it can be programmed over UART. The chip is so simple that I tried to build a minimal system with a dead-bug circuit. As far as I know, it seems nobody has built a BLE circuit in this way. Maybe it is world first?

Components

1 × CH571K

2 × 0805 1uF capacitor

1 × 32MHz 1612 crystal

1 × LED with embedded resistor

1 × 3CM wire antenna

Project Logs

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Program the chip
deqing • 04/21/2025 at 18:40 • 0 comments

The chip can be programmed with Arduino.
The Arduino package is based on arduino_core_ch32. However the upstream is stall and I have to fork myself.
An up to date package can be installed from
https://github.com/DeqingSun/arduino_core_ch32/releases/download/arduinoPack/package_ch32v_index_add_ch573.json
There is BLE example (included in Arduino package) on https://github.com/DeqingSun/arduino_core_ch32/blob/add_ch573/libraries/CH573BlePeripheral/example/example_ch573_ble_test/example_ch573_ble_test.ino
You can either export binary and use WCHISPTOOL to flash the chip, or you can just select the Upload Method to "WCH-ISP" in Arduino IDE, and manually put chip into bootloader mode and flash it over USB (not on CH571K yet).
Note the example also include the USB-CDC code. That means if you are using a CH573/CH571 with USB port, you may simply choose the USB serial port in Arduino IDE and it can go into bootloader mode automatically, and do the flash. Just like Arduino Leonardo.
Here is video of the control over WebBluetooth, https://deqingsun.github.io/Javascript-Signal-Processing/bleFunctions.html

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Build Instructions

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Schematic of the circuit

Back photo

Solder tips

The exposed pad is connected to pin 3 GND internally. The two capacitors can be soldered directly from the exposed pad to pins 2 and 7 for decoupling.
The crystal can be soldered directly on pins 4 and 5.
The LED can be soldered between pin 1 and the exposed pad.
The antenna can be soldered on pin 6.
The FTDI connection GND pin can be soldered on the exposed pad for support, and the 3.3V, TX, and RX can be connected with wire.

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Dead-bug BLE LED blinky

Description

Components

Project Logs

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Program the chip

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Dead-bug BLE LED blinky

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