A tiny frequency probe plus OLED display with the ATtiny84 @technoblogy @MicrochipMakes
Technoblogy presents the design of a Frequency Probe, a handheld tool designed to help you debug your circuits by giving a visual indication of the frequency or voltage at the probe. For a periodic waveform it gives a digital readout of the frequency, with a range of about 1Hz to 5MHz and an accuracy of better than 0.3%. For a voltage level it gives a readout of the voltage. It is based on an ATtiny84A, and is powered from a small Lipo cell.
I chose the ATtiny84 for this project because it has an 8-bit Timer/Counter0, which you can clock from an external signal on T0, providing an accurate way of measuring an external frequency. It also has a 16-bit Timer/Counter1 with input capture, which copies the contents of the counter to a register on the rising or falling edge of the input capture pin, ICP1. This allows you to time the period of a waveform very accurately.
It uses the USI peripheral to drive an I2C OLED display and display the readings in double-sized characters, using a 6×8 pixel character font.
The project is laid out in detail with the code, parts, and PCB available on Oshpark.
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