1 week Ago By Al Williams
If you want to add humidity and temperature sensors to your home automation sensor, you can — like [Maker’s Fun Duck] did — buy some . For a dollar, you get a little square LCD with sensors and a button. You even get the battery.
Can you reprogram the firmware to bend it to your will? As [Duck] shows in the video, you can. The device advertises some custom BLE services, but [Duck] didn’t want to use the vendor’s phone app, so he cracked the case open. Inside was a microcontroller with Bluetooth, an LCD driver, a sensor IC, and very little else.
The processor is an ARM Cortex M0, a PHY6222 with very low power consumption. The LCD is a very cheap panel with no drivers onboard. All the drive electronics are on the PCB.
The sensor is a CHT8305C which uses I2C. Luckily, the PHY6222 has a publically available SDK with English documentation. The PCB has two sets of UART pads and it is possible to flash the chip via one of the UARTs.
Eventually, [Duck] put a custom firmware on the box, but we were intrigued by the idea that for a buck you could get a little low-power ARM module with an LCD and a sensor. It seems like you could do more with this, although we are sure the LCD is not very general purpose, surely this little box could act as a panel meter, a countdown timer, or lots of other things with some custom firmware. These are, of course, knock offs of the slightly more expensive Xiaomi sensors, and those are , too.
We aren’t sure how accurate either sensor is, but is a complex topic..
