this is a simple logic probe project based on TI EZ430 dongle. i took advantage of a free offer on a couple of ez430s from TI in september 2010. they are very handy and fun in trying out small code snippets and watch the led blink. they had since been laying around my desk and i have to come up with something for them. and i want to stop people coming up and ask to borrow my "memory stick".

well, this is no memory stick, 16bit MCU w/ multi-channel ADCs, adequate 2K programming memory and runs up to 16Mhz. all packed up with the debugging programming interface board in a nice usb device package.

my main design goal is to limit my intervention to the original ez430. in that i don't want do alter it too much physically and i want to retain it's programming / debugging function for other target board projects. all this while serve additional useful purposes.

this is a linux project, as usual, i had given attention with my best knowledge to make provisions so that it can be built under windows. however i do not have the time and resources to try out everything under windows.

most of my electronics projects are done on very small breadboards and i usually work on tight spaces (kitchen table, half a borrowed desk, etc). there are many instances that i need to check circuit logic levels and i've been using a multimeter (size of a brick) to check things out. it always annoys me as my projects are much smaller than my multimeter and i found it always gets in my way. i need an alternative, a small logic probe will do.

the ez430 is perfect for this task. to begin with, it's already shaped like a probe, i just need to add a nail and some leds. as i mentioned earlier, i want to make this project simple and non-destructive. and i made use of what's available already.

instead of building the project on a pcb / pref-board, i build this on a target msp430f2012 board, employing the 14 pin header thru holes as my prototyping area. this is where the tiny leds goes. i do not want to drill holes on the plastic casing, i don't want to run too many wire nor add additional contact points. all i need is a probe io contact and a button input for function select, plus gnd and vcc. the usb connection looks perfect for this task. i will power the probe via the usb (the programmer circuit will regulate a around 3v potential for me) and use the D+ and D- usb connects for my probe and switch.

since the ez430 is slave / client device, upon initialization, it won't do a thing except a pull-up on D+ (to indicate it's a "hi-speed" usb). i use the floating D- as my probe io and D+ as my tactile button input (i don't even need to setup a pull-up resistor for that, it's already there)

additional information can also be found here.

Step 1: Features and Application


* supply from circuit via usb connector
* 3 operating modes rotating between logic read, pulse output, pwm output
* long button press (about 1.5 sec) rotates through the 3 operating modes
* p1.0 original green led as mode indicator, off - probe, on - output, blink - pwm

logic probe

* logic probe red - hi, green - low, none - floating
* logic probe red / green blinks on continuous pulse reads > 100hz
* 4 yellow leds shows detected frequencies in 8 steps, blinking yellows indicate hi-range (i.e. step 5-8)
* shows detected pulse frequencies for 100hz+, 500hz+, 1khz+, 5khz+, 10khz+, 50khz+, 100khz+, 500khz+
* for non-continuous single pulse bursts, the red / green leds stays on and subsequent pulse counts are displayed incrementally on the leds, will count up to 8 pulses

continuous pulse output, frequency setting

* indicated by p1.0 original green led on
* 4 yellow leds shows output pulse frequencies in 9 steps, blinking yellows indicate hi-range (i.e. step 5-8)
* pulse frequencies output for 100hz, 500hz, 1khz, 5khz, 10khz, 50khz, 100khz, 500khz, 1mhz
* short button press rotates the 9 different frequency settings.

continuous pulse output, pwm setting

* indicated by p1.0 original green led blinking
* same as previous operation mode, except pwm values are show (and be setup) instead of frequency
* 4 yellow leds shows output pwm percentages in 9 steps, blinking yellows indicate hi-range (i.e. step 5-8)
* pwm percentages for 0%, 12.5%, 25%, 37.5%, 50%, 62.5%, 75%, 87.5%, 100%
* short button press rotates the 9 different pwm settings.


the schematic is made up from two parts, in which they are connected via a pair of usb connectors. the left side schematic shows additions to the EZ430 dongle with a F2012 target board. the right side schematic is the logic probe-head and is to be constructed from scratch.

Very clever and well done probe head.
Nice. Clean and simple. I like this one.

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