Hack Correlation

This is just a reiteration of my post on  http://www.eevblog.com/forum/ . Since then some people have picked up the challenged and designed new firmware for the microcontroller. Let me explain. The module is a cheap (2-3$) 0-30V voltmeter. It has a 3-digit output, is pretty accurate and begs curiosity with it's TXD/RXD soldermask labels. The inside sports an STM800S3F3 chip with nice features: 2.95-5.5V supply voltage 16 Mhz internal oscillator 3 timers 4 CCP/PWM modules 5-channel 10-bit ADC UART, SPI, I2C 8k Flash, 1k RAM Thoughtfully, the programming/debug port is also broken out, just not labeled. The pinout would then be:   SWIM / PD1 (HS)   TX / AIN5(HS) / PD5   RX / AIN6 (HS) / PD6   NRST   VDD   VSS The board also includes a 3V/30mA linear regulator that can take up to 30V. All-in-all a very cheap development board that can be used for a lot of stuff Here's a close-up picture of the board under strong light ...

Update: if you came here looking for a fix to the annoying beep I might have one - if you are feeling handy: take the unit apart, desolder one wire from the battery terminal, discharge the capacitor (by touching the disconnected wire to the other wire) and solder it back on. Take care not to short the battery, you only want to discharge the circuit with the battery disconnected. If you do not understand perfectly what you need to do then please do not attempt this! This has 'fixed' one of my units (since 6 months) and has quitened another one for ~2 months. Back to the original post: On of the my smoke detectors - installed by the landlord under legal obligation - started acting up by emitting annoying short beeps and random intervals, moreso during the night. The producer boasts a 10-year service lifetime, smoke detection as well as heat detection. Since they are the "non-user-serviceable" type nothing else remains than to take it apart and see wha...

I'm working on a small project in which I'm trying to find out if I can output a sound on a piezo while reading the force exerted on it. It's like a small piano where the input is also the output. I did something similar with LEDs where I measured the light level by first reverse polarising the led and then measuring the discharge time (capacitance). To have an idea with what levels I'm dealing some measurements were in order. Two sets of measurements were taken, one with the original molded plastic housing and one with the housing removed and two wires solder to the piezo. I'm using a normal buzzer, the cheapest I could find, so that I can buy several of them. Raw buzzers should be 10x cheaper than what I paid. This is a light tap on the table while the sensor is sitting about 1m away pressed against the table. The housing was on. Around 1Nm of force from a lighter. A stronger tap under the same conditions, around 5Nm. The same stronger tap...