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7.
Blinking a 3V LED with VDD at 1.8V
Following the instructions in the
section to supply VDDIO2 with 3.3V and VDD with 1.8V.
Make sure that VDDIO2 and VDD have the correct voltage levels by using a multi-meter.
Following the instruction in the
section, we check that VDDIO2 is within acceptable range
before starting the blinking.
Make sure the LED has a forward voltage of approximately 3V by using a multimeter with diode testing capabilities. A
green LED usually has a forward voltage of approximately 3V.
An external green LED in series with a resistor of at least 15 Ohms needs to be connected to PC0, like shown in the
figure below.
If a different LED is used, the resistor value needs to change. This is calculated using the following formula where
V
LED
is the voltage drop of the LED and A
LED
is current through the LED:
� =
�����2 − �
���
�
���
WARNING
The AVR DB can not be programmed below 2V, so to ensure proper operation, set VDD to 3.3V by
dragging and dropping the provided text file “VDD3V3.txt” onto the “CURIOSITY” drive on your PC. When
programming is done, lower VDD to 1.8V by dragging and dropping “VDD1V8.txt” to the “CURIOSITY”
drive. Both .txt files can be found in the GitHub repository linked in the introduction.
Figure 7-1. Curiosity Nano AVR128DB48 - LED Circuit Physical Layout
R1
D1
External
voltage
Supply
3.3V
On-board
voltage
regulator
Resistor remains
removed as described
in HW Configuration
TB3287
Blinking a 3V LED with VDD at 1.8V
©
2020 Microchip Technology Inc.
Technical Brief
DS90003287A-page 15