JHE42B and JHE42B_S open firmware

The goal of this project is to replace the default firmware of the JHE42B and JHE42B_S buzzers, which use the STM8S003F3 chip, with a custom firmware that introduces common features found in other autonomous buzzers, especially the ability to disarm the buzzer without using the onboard button.

Features

(checked if implemented)

• BEEPS every 30s after power loss (default)
• Turn ON/OFF onboard red LED depending on arming status (ON when armed)
• Disarm system when button is pressed
• Disarm if power supply is removed after 10-12s if armed (usefull when button is not accesible)
• Power saving by changing BEEPS frequency 10s / 30s / 60s (default 30s)
• BEEPS on signal pin request
• LIGHT flashs for every beeps (built-in)

Board testing matrix

Model	BEEPS on power loss	Arming Red LED	Button disarm	Power source trick disarm	Power saving	LED Flash	BEEPS on signal
JHE42B	✔️	✔️	✔️	✔️		❌	✔️
JHE42B_S	❔	❔	❔	❔		❔	❔

❌ ko / ✔️ ok / ❔ todo or more testing required

User manual

1. Arming the Buzzer:
   • Apply power to the buzzer to arm it. You will hear a 3-note arming sequence and see the red LED turn ON.
2. Alarm:
   • The buzzer will beep every 30 seconds after power is lost.
3. Disarming the Buzzer:
   • Long press the onboard button 3 times (you hear1-note when press is registered), or
   • Apply power for 10 seconds and then remove it.
   • You will hear a 3-note disarming tune, and the red LED will turn OFF.
4. Rearming:
   • After disarming, the buzzer needs to be power cycled to be rearmed.

How to Build/Flash

Requirements

• vscode or any IDE supporting PlatformIO
• ST-link v2 (so you can write firmware onto the STM8 flash memory) how to connect it?

PlatformIO setup

• Follow instruction of platfomio-ststl8
• clone the repo and open the project in vscode/pio
• PlatformIO should download and install all the toolchain/dependencies
• build
• upload/flash

Otherwise add board definition stm8s003f3.json in :

C:\Users<user>.platformio\platforms\ststm8\boards

Unlock chip

Every chip has to be unlocked once. (from experience)

cd .platformio\packages\tool-stm8tools
stm8flash -c stlinkv2 -u -p stm8s003?3

STMLinker connection

Connect the wires to the linker as shown below.

Alternatively, if you don't want to solder on the board, you can use a setup like this:

+

Compatible Boards

Model	Controller	Chip Mark	Pictures
JHE42B	STM8S003F3 TSSOP20	STM8S003F3P6
JHE42B_S	STM8S003F3 UFQFPN20	S033PHVG822Y

Commercial shot

Reverse Engineering Process

(checked if working)

• power supply detection
• blink onboard red LED
• blink onboard white LED
• bip on buzzer
• button press

Resources

ST STM8S003F3 DataSheet ST STM8 debug