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Input Devices
2 © tjEE 4980 – MES
Input Devices
• Keypad
3 © tjEE 4980 – MES
Input Devices
• Keypad
PT0 PT1 PT2 PT3
PT4
PT5
PT6
PT7
Port[0:3] = InputsVdd
Port[7:4] = OutputsPull one of
PT4, PT5, PT6, PT7 low
If a key is pressedThe associated PT[3:0] inputwill be pulled low
Scanning:Cycle through the outputs, check the inputs
4 © tjEE 4980 – MES
Input Devices
• Keypad
PT0 PT1 PT2 PT3
PT4
PT5
PT6
PT7
Port[0:3] = Inputs with pull-up turned on
Port[7:4] = OutputsPull one of
PT4, PT5, PT6, PT7 low
If a key is pressedThe associated PT[3:0] inputwill be pulled low
Scanning:Cycle through the outputs, check the inputs
5 © tjEE 4980 – MES
Input Devices
• Keyboard
• N x M matrix of switches
6 © tjEE 4980 – MES
Input Devices
• Keyboard
• N x M matrix of switches
7 © tjEE 4980 – MES
Input Devices
• Keyboard
• Mechanical Switches
8 © tjEE 4980 – MES
Input Devices
• Keyboard
• Mechanical Switches
9 © tjEE 4980 – MES
Input Devices
10 © tjEE 4980 – MES
Input Devices
• Keyboard• Controller
11 © tjEE 4980 – MES
Input Devices
• Keyboard
• Controller
• Performs debounce – 1-5ms typical
• Polling rate - < 200Hz
• Interface – USB, wireless, SPI, TWI
12 © tjEE 4980 – MES
Input Devices
• Mouse
• Opto-Mechanical
13 © tjEE 4980 – MES
Input Devices
• Mouse
• Opto-Mechanical
14 © tjEE 4980 – MES
Input Devices
• Mouse
• Opto-Mechanical
15 © tjEE 4980 – MES
Input Devices
• Mouse
• Opto-Mechanical
16 © tjEE 4980 – MES
Input Devices
• Mouse
• Optical Mouse
17 © tjEE 4980 – MES
Input Devices
• Mouse
• Optical Mouse
18 © tjEE 4980 – MES
Input Devices
• Mouse
• Optical Mouse Sensor
• By comparing images – direction and distance can be calculated
19 © tjEE 4980 – MES
Input Devices
• Mouse
20 © tjEE 4980 – MES
Input Devices
• Mouse
21 © tjEE 4980 – MES
Input Devices
• Mouse
22 © tjEE 4980 – MES
Input Devices
• Mouse
• Optical Mouse Sensor
• Output is a quadrature signal - just like a mechanical mouse
23 © tjEE 4980 – MES
Input Devices
• Mouse
• Optical Mouse Sensor
• Frame Rate: 1500 frames/sec
• Typical resolution: 400-800 cpi (counts/inch)
• Speed: 14ips (inches per second)
• Typical sensor dimension: 16x16 to 32x32
• Typical Path error: 0.5%
24 © tjEE 4980 – MES
Input Devices
• Mouse
• Optical Mouse Sensor
• Limited focal range
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