LEDs and Switches
STK600 has eight LEDs and eight switches that can be connected to I/O pins on the AVR. The LEDS and SWITCHES connectors are found in the
port connector area.
LEDs
The LEDs are labeled LED0 to LED7. The corresponding pins on the LEDS header have the same labels.
The LED hardware is shown in the figure below. The transistor circuit ensures the LED brightness is independent of target voltage.
To light one of the LEDs, the corresponding pin found on the LEDs header must be pulled to GND.
To control the LEDs from the AVR, connect a cable between the LEDS header and one of the PORT headers. Use a 10-wire cable to connect to all
eight LEDs or a two-wire cable to control one or two LEDs.
Just like the PORT headers, the LEDS header has GND and VTG on pin 9 and 10. When using a 10-wire cable, make sure the pin one indication on
the cable (red wire, triangular arraow pointing on pin one) aligns to pin 1 on both the LEDs header and PORT pin header.
The I/O port connected to LEDn will not source any significant current when LEDn is driven high, but it will sink a current of approximately 18mA
when LEDn is pulled to GND.
Switches
The switches are labeled SW0 to SW7, and are available on the SWITCHES header. The switch hardware is shown below:
When pressing one of the switches, the corresponding SW pin on the SWITCHES header will be pulled low. When the switch is released, the
switch's 10k pull-up will pull the line to VTG. The 150 Ohm resistor prevents a large current to flow to ground in case of wrong wiring.
Connect a cable between the SWITCHES header and one of the PORT headers. Use a 10-wire cable to connect to all eight switches or a two-wire
cable to connect to one or two switches.
Note: On most AVR pins configured as input, you can enable an internal pull-up, removing the need for an external pull-up on the push button. In
the STK600 design, an external 10K pull-up is present to give all users a logical '1' on SWn when the push button is not pressed, even if the internal
pull-up is not enabled.
Clock Settings
VCCIN, VBOOST, VCC0, VCC2, VCC3, VCC5, VCC6, VCC7 VTG
Page 19 of 35
STK600 User Guide
2008-06-20
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