Integrated circuits within telecommunications and industrial electronic devices and complex consumer devices (for example, in a TV set) often communicate using the I2C protocol. This article describes a simple device that can monitor traffic on the I2C bus. Let’s find out what kind of messages these chips exchange!

Not long ago, I was testing a PWM power supply and its characteristics. For basic tests, an ordinary 100W ceramic power resistor – a souvenir from my student days, was enough. Finding a similar resistor nowadays would be nearly impossible task. Probably one can find it at radio amateur “flea markets”. Even if we found a suitable resistor, this is not a good solution if we want to perform measurements over wide range power supply voltages/currents. For that purpose one would need to buy either a powerful rheostat or a programmable electronic load.

The ATtiny2313-based frequency meter shown in Figure 1 can measure frequencies from 1 Hz to almost 10 MHz with a 4 to 5 digit accuracy. The accuracy depends primarily on the exact frequency of the X1 crystal, which can be fine-tuned by the variable capacitor C5. A 74HCT4520 (IC3) is used as a digital low-pass filter, which signals the microcontroller if the measured frequency exceeds the upper limit. A two line LCD display is used to show the result. Therefore, the frequency and the period can be displayed simultaneously.

The RFM12B expansion board offers MiniPin II and MegaPin users a cheap platform for developing short-range RF communication using RFM12B transceiver modules. The RFM12B is a low-power version of RFM12 module. It operates from 2.2 to 3.8 Volts.

Did you ever want to discover a hidden treasure? One of the first devices that I built as a child was a simple metal detector. Later, I built various different metal detectors from plans published in electronics magazines. Today, the prices for metal detectors vary from a few hundred to a thousand Euro, and therefore I have decided to design one of my own – an improved version of the “pulse induction” metal detector.