Gadget Freak

More inspiration for designing your own circuits - the three latest Circuit Design Ideas that have been added to the site.

They involve implementing a touch-switch decoder with no external components, a simple RS-232-to-TTL converter that tests UARTs using a PC's serial port for power, and a bit-shifting-based method for fast integer multiplying, and multiplying by fractions.

Capacitive touch switch uses CPLD, courtesy of Rafael Camarota, Altera, San Jose, CA; Edited by Charles H Small and Fran Granville

RS-232-to-TTL converter tests UARTs with a PC, courtesy of Matthieu Bienvenüe, Malissard, France; Edited by Charles H Small and Fran Granville

Bit-shifting method performs fast integer multiplying by fractions in C, courtesy of Aaron Lager, Panamax Furman, Santa Rosa, CA; Edited by Charles H Small and Fran Granville

Capacitive touch switch uses CPLD
Capacitive touch switches work by measuring the change in capacitance of a PCB (printed-circuit-board) pattern depending on the placement of a user's finger over a sensing pad.

Capacitive switches are becoming popular because they are less expensive than mechanical switches. Using the features of an Altera MAX IIZ CPLD (complex-programmable-logic device), you can implement a touch-switch decoder with no external components...
Read the full Circuit Design Idea


RS-232-to-TTL converter tests UARTs with a PC
You often need an RS-232-to-TTL adapter for debugging or testing UARTs using a computer. But most of these adapters require an external power-supply adapter to power up the RS-232 transceiver.

This external adapter increases the number of cables on your desk and uses no flow-control signals...
Read the full Circuit Design Idea


Bit-shifting method performs fast integer multiplying by fractions in C
This Design Idea presents a method for fast integer multiplying and multiplying by fractions.

What can you do when you lack access to a hardware multiplier or MAC (multiply/accumulate) function and you need to multiply by something other than a power of two?...
Read the full Circuit Design Idea