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44 votes

Mac OSX Yosemite no serial ports showing for Uno R3

Probably, you have Chinese Uno analog which works on CH340 USB-to-serial chip, so you need to install driver for it. Steps to fix: Install the CH340 driver Run the command in Terminal: sudo nvram ...
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  • 541
39 votes

First time set up- permission denied to usb port- ubuntu 14.04

From the documentation: Open Terminal and type: ls -l /dev/ttyACM* you will get something like: crw-rw---- 1 root dialout 188, 0 5 apr 23.01 ttyACM0 The "0" at the end of ACM might be ...
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17 votes
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Can the Arduino interface with USB devices without the USB host shield?

First things first you need to learn the basics of how USB works. In USB there are two main "things": Hosts and Devices. You have one Host (usually your computer) and many Devices (such as Arduinos, ...
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15 votes

Mac OSX Yosemite no serial ports showing for Uno R3

The cable that shipped with my Arduino Uno worked for power but not data transmission so the /dev/tty.usbmodem was not showing up in the Tools --> Port menu. After I switched to a different cable, the ...
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  • 151
15 votes

If the USB gives 5v, how can the Arduino supply 5v to the 5v pin? (And another question)

Actually, Arduino is powered at 5V (the 5V pin and the ATmega328p are connected to the +5V rail in the board). The point here is where do those 5V come from. Basically, from 2 possible sources: USB. ...
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  • 2,102
13 votes
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Arduino Nano no serial port for MacBook Air 2013

This solved it for me. Download this driver Install it Run sudo nvram boot-args="kext-dev-mode=1" Reboot Serial ports now showed up in the Arduino IDE and also when I used ls -1 /dev/tty* Hopes ...
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  • 391
8 votes
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How to stop Arduino from drawing power through USB

If you provide power to the Arduino through Vin this will disconnect USB power through the MOSFET switch.
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  • 1,645
8 votes
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Difference between /dev/ttyACM0 and /dev/ttyS0 (Arduino IDE ports under Linux)

/dev/ttyACM0 is a USB communication device (CDC) of sub-type "abstract control model" (ACM). That is what the Arduino is. /dev/ttyS0 is a hardware serial port - the (typically) 9-pin D connector on ...
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  • 103k
8 votes

Arduino Nano not visible in Serial Ports (Mac OS)

Is it an original Nano or a clone? The original Nano uses FTDI's FT232 ship, whereas clones use the CG340 USB-to-TTL chip. The former works fine straight away Mac OS Sierra, whereas the latter needs ...
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7 votes
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External 5V Power and USB Serial

Having used counterless Arduinos and clones, I can tell you that you can connect both without worrying about any danger. Unless you have a very faulty board, your pc won't be damaged, almost surely ...
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  • 303
7 votes
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CH340 max serial speed

CHG340 supports common baud rates: 50, 75, 100, 110, 134.5, 150, 300, 600, 900, 1200, 1800, 2400, 3600, 4800, 9600, 14400, 19200, 28800, 33600, 38400, 56000, 57600, 76800, 115200, 128000, 153600, ...
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  • 1,296
6 votes

Powering an Arduino Mega with external USB Power Bank?

I have a "USB power bank" with two USB ports, which I use to power some projects. I have discovered that my bank (i.e. your mileage may vary!) shuts off unless my project draws at least 50mA. If your ...
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6 votes

Mac OSX Yosemite no serial ports showing for Uno R3

This fixed the problem for me: http://blog.sengotta.net/signed-mac-os-driver-for-winchiphead-ch340-serial-bridge/ ... and the direct link to download. EDIT: I have one of the cheap clones with a ...
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6 votes
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Is it OK to Serial.print(message), when the USB cable is not connected to a host PC?

It is OK to write out serial data with nothing connected. In case (2) "Arduino + USB interface chip", the arduino has no idea if anything is connected or listening to the serial port. The ...
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  • 4,309
6 votes

First time set up- permission denied to usb port- ubuntu 14.04

All you need to do is add yourself to the dialout group as described in the answer by Ignacio Vazquez-Abrams. This is done in the terminal by typing: sudo usermod -a -G dialout $USER You do not need ...
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6 votes

My Digispark board won't show up in Ports tab in Arduino IDE (OSX)

I don't think it is supposed to. The Digispark briefly connects in "bootloader" mode, which you spotted as "Vendor-Specific Device:". Then after 5 seconds it runs the loaded sketch. If your sketch ...
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  • 35.3k
6 votes

Arduino Leonardo as keyboard for an iPad

If indeed the descriptor is the problem then yes you can change it. In the core file USBCore.h is the line: #define D_CONFIG(_totalLength,_interfaces) \ { 9, 2, _totalLength,_interfaces, 1, 0, ...
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6 votes
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How can I detect which baudrate a virtual COM port is set to?

From looking at the source it appears that on 32u4 based boards Serial includes extra methods to access the settings from the USB host: see: https://github.com/arduino/ArduinoCore-avr/blob/...
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5 votes
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Can I simply unplug the Arduino usb if serial communication is active?

if the sketch is uploaded, it wont hurt it to unplug. Just give it another source of power and it will run its sketch.
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5 votes

Mac OSX Yosemite no serial ports showing for Uno R3

Yosemite 10.9 (and OS X 10.10 and newer) requires a signed USB driver kext (kernel extension). You can find one on the FTDI web site here: http://www.ftdichip.com/Drivers/VCP.htm Use version 2.3 for ...
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  • 279
5 votes

Mac OSX Yosemite no serial ports showing for Uno R3

This site fixed the problem for me: http://kiguino.moos.io/2014/12/31/how-to-use-arduino-nano-mini-pro-with-CH340G-on-mac-osx-yosemite.html ...somebody else has made an alternative to the ftdi ...
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  • 59
5 votes

Keyboard.print() skips keys

The Arduino assumes a US keyboard layout. The thing with keyboards is they don't actually send the letters or symbols that are printed on the keys. Instead the send a scan code that defines where on ...
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  • 103k
5 votes
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Pinout for Leonardo USB

The USB does not go to pins 0 and 1. The UART goes to pins 0 and 1 - that is a totally different interface. The USB is connected to dedicated USB pins on the chip. If you look at the Leonardo ...
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  • 103k
5 votes

Protecting your computer from stupid (arduino) mistakes

Both the arduino and a USB port do have some protection against wrong connections and such. The arduino has a diode to prevent wrong polarity to reach your power supply, it also have a resetable fuse (...
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  • 474
5 votes

Why is there already text in the serial monitor before the Arduino initializes?

It's because the Arduino has started running the sketch and placed data into the USB chip's buffer. You then open the serial monitor which then opens the serial port thus resetting the Arduino. So the ...
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  • 103k
5 votes
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Which Arduinos have a true serial port?

There seems to be quite a few Arduinos without a 32U4, like: Uno (you mentioned it already) Mega (same) Lilypad Snap MKR1000 Pro Pro Mini Zero Due Ethernet Mini Nano MKR Zero See the list at ...
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5 votes

How to convert USB to PS/2?

Many USB keyboards (certainly older ones, though almost certainly not wireless ones) are also PS/2 keyboards. The wiring of the cable is all that differs, and the chip in the keyboard changes its ...
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  • 103k
4 votes
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Can an Arduino Micro receive commands from another microcontroller when hardwired together?

You cannot do this with the micro USB ports. You will need to use I/O pins. Either serial or I2C would be good options. It might be advisable to use I2C if you want to control multiple 'slave' ...
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4 votes
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Regarding the USB port, what is the difference between Uno/Mega and the older boards?

The older Arduino boards used an FTDI FT232R chip to handle the USB port. This chip is a special purpose, USB to serial UART interface. In the current Arduino boards, the USB to serial conversion is ...
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  • 146
4 votes

Mac OSX Yosemite no serial ports showing for Uno R3

This exact same thing happen to me on my mac running the same operating system. I had to restart this system a few times to get it to work. I restarted it with the arduino plugged in; and that worked ...
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