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digitalWrite HIGH & LOW inverted #16
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Same here |
Some of those boards have the LED connected to VCC, probably because the MCU can sink more (the needed) current in the I/O pins at lower level. |
I got the same issue , set LOW led is on. and digitalWrite(relayPin, HIGH); // Led OFF i tested both on D0// 16 , and D7 // 13 very confusing about this ? |
This is the wanted behaviour. If the LED would need a current of 20 mA for full brightness and you would connect the anode of the LED to the GPIO, the GPIO couldn't provide the needed 20 mA, as it can only provide 12 mA. If you turn it vice versa and connect the cathode to the GPIO and the anode to the main 3.3 volts power supply (which should be able to provide about 800 mA of current), you can reach the full brightness (and save your GPIO). But then, the LED lights up, when the GPIO is set low. |
Thanks for your information that helped. @pathob |
Just to be clear, is normal for every Digital PIN do be inverted or just the pin LEDs ? |
Same problem with digitalWrite(ledPin, 0); //Turn led ON |
Very common practice to do this. Find a schematic for the LED on the circuit board you are using and you'll see how it's biased for the I/O. If this is difficult for you to remember then there are ways around the confusion. Someone once said that good code reads like a story. Coding in C is not an elegant story... // My pet's name // My pets mode // Your pet's tricks digitalWrite(Red_LED, turn_On); You could get really crazy and write a function... void RED_LED( string action ){ RED_LED("ON"); I would dig into the pins_arduino.h file and see if there is a definition for the LED on that GPIO and use that reference. It's a good practice to do that because it makes your code more portable. |
How can i make my external led that also connected to GPIO16 turn on and turn off in sync with my internal red led? My brain can not process this logic. When i set my external led off, my internal led is on... and they both can not do what i say. pinMode(16, OUTPUT) and digitalWrite(16, LOW) also not working, i mean, may be i can turn the external led on just like the internal one by connecting the external led anode to 3.3v rail and cathode to pin 16 with that piece of code, but... its just not working. Please help me. |
I'm sorry, problem solved. My imperfect sensor in my face didnot see the NodeMCU pin is not really click to breadboard. This silly things make me crazy for six hours. The code is right, just need to push the Node to breadboard. hahh.... |
Best fix ever! |
Thank you! I spent waaaay to long being confused as hell before googling it... |
Dear All, |
found this article which explains it in detail: https://www.dataq.com/blog/data-acquisition/whats-all-this-sink-and-source-current-stuff/ |
After searching about this for a while.. i found the reason for this kind of behaviour in ESP8266 board.. Solution for this problem is.... So please use the correct GPIO pins for input and output..try to use pins that are marked green only....thank you.. |
Once we give low input to pin 16 of NodeMCU ESP8266, it remains low, see my code below which is not able to switch off led because of this issue, can't we use pin 16 as general purpose input? |
Hi guys, have a look at this great post https://www.instructables.com/ESP8266-Using-GPIO0-GPIO2-as-inputs/ |
Hello!
Let me get this straight. I bought the following board:
http://www.aliexpress.com/item/Free-shipping-NodeMCU-development-board-for-ESP-12E-from-ESP8266-esp-12E-Lua-IoT-programable-wifi/32583355412.html
I use the Arduino IDE, and everything works pretty much fine. I only have one problem:
If i test it for the blink sketch it reads HIGH as LOW and LOW as HIGH.
Example:
[code]
void setup() {
// initialize digital pin 16 as an output.
pinMode(16, OUTPUT);
}
// the loop function runs over and over again forever
void loop() {
digitalWrite(16, HIGH); // turn the LED on (HIGH is the voltage level)
delay(1000); // wait for a second
digitalWrite(16, LOW); // turn the LED off by making the voltage LOW
delay(100); // wait for 1/10 second
}
[/code]
This should do (as far as i know) that the LED is on for 1 second and then have a short pause of 1/10 second.
But what the board is really making is the opposite. The LED is off for 1 second following a short blink 1/10 second and so on...
Am I insane or is this plain inverted?
I'm on a mac with Arduino IDE 1.6.8
I use the following bridge drivers:
https://www.silabs.com/products/mcu/Pages/USBtoUARTBridgeVCPDrivers.aspx
Thank you for answers!
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