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Stop-Watch x10 from Smart Response PE

You may never need 10 stop watches at one time, but if you do, this hacked PE device was crafted for you.

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It has a numeric keyboard and room to display 10 time units in MM:SS.xxx format. Projects falls into the "because I can ..." category.


Sometimes there is no good reason to pursue a project other than it seems like fun; even when completed, it may be difficult to describe the intended use.  This is one of those projects: a surplus Smart Response PE candy-bar style device with a TI CC2533 uC, a LCD, and a numeric keypad and a few control keys.  

This comes on the heels of my previous Smart Response PE project which created a RPN calculator.  This project uses the same foundational software environment and similar code structure.  Written in C89'ish style, the core hardware libraries by Github user serisman allows for an arduino-like programming experience;  excepting the background preprocessing magic performed by the ArduinoIDE, for example, automatic prototyping of functions.

Implementation

Only the 0-9 numeric keys, the ENTER key, and the Home key are utilized.  Pressing 0 - 9 will activate (link) the stopwatch timer to the internal millisecond clock.  The timer will be located on the LCD in the following order:

( 1 )           ( 2 )

( 3 )          ( 4 )

( 5 )          ( 6 )

( 7 )          ( 8 )

( 9 )          ( 0 )

and each will be in the format:  MM:SS.xxx where the behind-the-scenes HH: is masked due to minimum LCD real estate.

The ENTER key: 

ENTER

will pause the LCD display (not the timer counting) until pressed a second time to resume the LCD display.

The HOME key:

Home

Does a reset on all timers, clear the LCD screen, and essentially does a soft-reset for new usage.

Notes and Considerations

Some (quick) empherical testing was completed during the software writing to determine how to minimize delay in linking the immediate keypress to the software variables used for the 10 timers; that is, an emperically constructed numeric constant was implemented depending on where the key ( 0 - 9) was implemented in the keyboard scan matrix and within the "switch/case" statements.  These constants are approximately 1mS different from key-to-key and in actuality use have no apparent bearing on the common usage of the device.  Of course, until implemented, the impact was unknown and in hindsight was essentially a waste of time!

StopWatch.zip

ZIP containing all source files and batch files to semi-automate SDCC's compile, link, and convert-to-HEX operations.

x-zip-compressed - 111.01 kB - 07/04/2023 at 13:55

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main.c

For quick view: included with the ZIP

C Source File - 6.32 kB - 07/04/2023 at 13:54

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  • Visual & Notes

    Ray Burne07/07/2023 at 00:42 0 comments

    Pictures of major mechanical modifications:

    Addition of real power switch.  The spring contacts at the bottom of the battery compartment were separated (cut) and slightly shortened; then the wiring to the switch was soldered to the spring contacts. Note, a good roughing with fine abrasive paper and the use of a quality flux will greatly assist with soldering.

    Note that holes were drilled in the plastic ribs to easily route the wires.  After soldering to the push-locking switch, use an Ohm meter to verify you have correctly wired the switch.  Hot-melt glue can secure the switch and is preferable to "super glue" which can wick into the switch and damage it.

    I used a Dremel tool to drill a small hole directly where the elastic-power (soft switch) was located.  The LED can be secured with UV adheasive, hot-melt glue, or quick-set 2-part epoxy.  A 1K Ohm resistor was used for current limiting; select based upon LED color.

    The LED and resistor are wired directly to the upper battery spring contacts on the circuit board.

    On the case face plate, I used a drop of UV clear acrylic to form a lens and to plug the hole where the original rubber plunger was located.

    For this mod, I wanted to extend the programming to rolled-pins mounted under the battery cover.  This is not particularly difficult, but is somewhat tedious.  The pins were removed from a quality DIP IC socket and held in place using Kapton tape across the back battery compartment.  The pins are positioned with forceps from the back and carefully pressed against the tape to secure a liquid seal.  Then a few drops of UV adheasive will set the pins until the hot-melt glue permanently secures the assembly.

    Just the soldering of the jumpers to the system board and case reassembly remains.

    Satisfaction for a completed mod.

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