I just got an arduino nano and I am trying to power a LED.
Just for test I ran the led blink tutorial (http://www.arduino.cc/en/Tutorial/Blink)
However, if I try to measure the pin 13 (D9) I read ~0.20V even when the pin is supposed to be off. I do see the led on the board blinking so I know my program is working properly.
I thought it might be because of the pin so I tried quite a few others and same result.
I also tried an analogWrite with different values and I still read the same voltage.
I triple checked the pinMode to make sure it's on OUTPUT.
If I measure the 5V pin (between A7 and RST) I can read 4.2V which is compliant with the spec.
I am truly at lost now and I don't know how to troubleshoot this.
Thank for any help
How are you powering the Nano? Are you using USB? Are you feeding 5V into RAW? The 5V pin should measure very close to 5.0V relative to the GND pin.
The "L" LED is connected to the pin labeled D13. It's not clear that you meant D13 when you said "if I try to measure the pin 13 (D9)".
The PWM (analogWrite()) pins use Pulse Width Modulation (actually duty-cycle modulation) to control the average voltage. For values other than 0 and 255 they are pulsing 500 to 1000 times per second. That can confuse some methods of DC voltage measurement.
At first I thought you didn't understand my question, but then I realized the problem was that I didn't understand how to read the schema.
I thought the number passed to digitalWrite refered to the pin number as we can see on the schema http://www.arduino.cc/en/uploads/Main/ArduinoNano30Schematic.pdf
I thought that writing digitalWrite(13, HIGH) would power up D9, because the pin 13 is D9.
I now understand that the number in the function refers to the label D13 and not the pin 13.
Thank you for your response!
I'm having similar issues with my Arduino Lilypad. Some of my digitalWrite(x,LOW) functions output 0.5V above ground for two of my pins, while they get closer to zero for the other pins. Where can I check if that's within spec?
The data sheet, section 29.
With low current amounts it will be lower, with high currents it will be higher.
Although each I/O port can sink more than the test conditions (20mA at VCC = 5V, 10mA at VCC = 3V) under steady state conditions (non-transient), the following must be observed:
ATmega48A/PA/88A/PA/168A/PA/328/P:
1] The sum of all IOL, for ports C0 - C5, ADC7, ADC6 should not exceed 100mA.
2] The sum of all IOL, for ports B0 - B5, D5 - D7, XTAL1, XTAL2 should not exceed 100mA.
3] The sum of all IOL, for ports D0 - D4, RESET should not exceed 100mA.
If IOL exceeds the test condition, VOL may exceed the related specification. Pins are not guaranteed to sink current greater than the listed test condition.
You do have a current limit resistor in series with the LED, yes?