“Logic Meter is a piece of electronic test equipment meant to make certain functions of a logic analyzer as easy to use as a multimeter. You can see a demo at https://youtu.be/55UjsmX5F90
It looks like a multimeter: it’s handheld, battery operated, has a display, has a knob for selecting the measurement you want to make, and has a set of buttons for navigating a menu to set options (e.g. setting the baud rate for the UART “measurement”).
But unlike a multimeter, the logic meter’s probes are for digital signals only (max. 5 volts) and the “measurements” are the sorts of things you’d do to test a microcontroller-based system.
The currently implemented measurements are:
UART In: connect two of the logic meter’s probes to ground and a UART signal, and the logic meter will display the UART data on the screen.
UART Out: send canned data out one of the probes in UART format. The logic meter has the ASCII set built in as one choice of canned data. Files can be copied over to the logic meter via USB and used as alternative canned data.
SPI In: connect three or four of the probes to GND, MOSI, CLK, and (optionally) SS, and the logic meter will display the SPI data on the screen.
GPS Simulator: the logic meter will send GPS data (NMEA sentences) out one of its probe wires. There is not GPS in the logic meter, so this is simulated data. You can set the time, longitude, and latitude. The logic meter draws a map of the Earth on the display and you can move a cursor to indicate the location you want to simulate.
Servo: the logic meter will send a 50Hz square wave out one of its probe wires. The user can change the duty cycle. This signal can be used to control a servo motor.
PWM: the logic meter will send a square wave out one of its probe wires. The user can change both the frequency and the duty cycle.
LED Test: put an LED in the LED socket and the logic meter will graph the forward current versus forward voltage on the display. You can then adjust the amount of current going through the LED and see how bright it is. This helps you decide how much current you want flowing through it and calculate a current-limiting resistor accordingly.
Logic Analyzer: the logic meter will sample values on the three inputs and display traces on the display. Triggers can be set for rising, falling, or either edge, on any of the inputs.
Utility: Enables the logic meter’s USB interface. Also could allow (in the future) for setting various configuration options or controlling the logic meter remotely.
The rotary switch used in the current design has one unused position, to add additional features.
This repository contains the hardware design and the firmware. This Readme file contains helpful information in understanding them.
It is my hope that someone will take this design, or at least this idea of a logic meter, and turn it into a mass-manufactured product. If you do this, I only ask that you contact me and let me know. I would like to be able to buy a professionally made version of this. You can contact me through my GitHub account, galacticstudios, or my website, GalacticStudios.org.”