Question

An embedded system incorporates an MSP430F2274 clocked by a 4.096MHz
at 3.3V, driving two seven-segment displays and two discrete LEDs. The sevensegment
display draws 7.5mA per segment at 1.8V and the discrete LEDs
operate with 10mA each at 1.6V. Three push-buttons are needed for completing
the user interface. Design a suitable interface to connect all LEDs,
seven-segments, and push-buttons. Estimate the circuit power requirements
and recommend a non-regulated power supply and a suitable regulator.

Answer 1

Major components required for design

1. Msp430 evaluation kit(MSP-EXP43042)

2. Octal buffer- 74ls244

3. 7 segment design- lt543

4. Discrete leds- Ati-3rdgn-l

5. Push button- ds1041-01-1-1-Kka-160-10

6.miscellaneous components like wires

Circuit uses a parallel interface using 2 sepearate octal buffers for each 7 segment displays

Sample design file is uploaded as image(for evaluation kit info, please search TI site.It contains full schematics and design file)

Note : push buttons are available in evaluation ki itself

If more user control is needed, u can use it in between buffer and display

Power calculation

Current to 1 display = 7.5*7 = 52.5ma

Total current to 2 displays = 52.5* 2= 105ma

Total current to 2 discrete leds = 10*2= 20 ma

So total current consumption= 20+105= 125ma

Total power= 3.3* 125ma = 0.412w

Total current consuption will be higher than calculated as there will be losses and consumption in buffer etc.

For power supply you can use a standard LDO 3.3 V, 500ma- ua78m33cdcyr