Last week s project demos
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Last week’s project demos. Servo control with photoresistor and enable/disable buttons Demo in class tonight – don’t start on the next project until I’ve seen this one!. More circuit design. Seven segment display. The Seven-segment Display. Nothing more that 8 LEDs in a single package

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Last week’s project demos

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Last week’s project demos

  • Servo control with photoresistor and enable/disable buttons

  • Demo in class tonight – don’t start on the next project until I’ve seen this one!

More circuit design

Seven segment display

The Seven-segment Display

  • Nothing more that 8 LEDs in a single package

    • Each LED can be turned on/off independent of all others

The Seven-segment Display

  • Like individual LEDs, each has a cathode and an anode leg

  • The anode of each LED is routed to its own pin on the package

  • All cathodes are connected together and routed to two pins on the package (choose one of the other)


  • The schematic shows the part as seven separate LEDs (as expected)


  • Use them as seven separate LEDs

  • That is, for whatever you would normally use an LED for

Typical circuit schematic and layout

  • See chapter 7 for example code

    • It’s just a bunch of OUTH and PAUSE statements

Memory usage

  • So far we have been writing to individual pins on the Basic Stamp module

  • For the seven segment display it would be convenient to write to multiple pins at one time

  • The I/O pins are memory mapped to various PBASIC Word type instructions

    • INS, OUTS

    • These are broken down further to Byte type instructions

      • INL, INH, OUTL, OUTH (Low byte, High byte)

      • These are broken down further to Nibble type instructions


        • These are broken down further to Bit type instructions

          • IN0 – IN15, OUT0 – OUT15

  • Utilizing these instructions will set the direction of the pin accordingly

Memory usage

  • Another instruction called DIRS (and all size variations) is available to set the directions of the I/O pins

  • We saw this earlier when we needed to “disconnect” an output pin

    • Set the bits to 0 for input direction

    • Set the bits to 1 for output direction

    • Default power up is input

  • This is useful when setting up to do I/O without actually doing the I/O operation


  • By changing the value of the capacitor the time decay can be altered

    • Book labs had you do this

  • For this assignment

    • Build RC circuits using both 0.1uF and 0.01uF capacitors to create 2 timers (select one resistor value)

    • Include a button to select one of the two timer s

      • Include debug statements to indicate timer decay

    • Use the bidirectional LED to indicate which timer is selected

      • Green – fast (short time decay)

      • Red – slow (long time decay)

    • Include a 7-segment display in your design in some creative way


  • Due next week

    • A functional description of the system

    • A state-machine diagram depicting the operation of the system

    • Source code

    • A schematic diagram of the circuit

    • A working demonstration on the Basic Stamp development board (in class)

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