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8 votes

A question about resistance measurement with arduino

If you know Ohm's Law (which you should) and you realise that the ADC measures voltage, you should be able to work it out from there. But I will go into minute detail for you to ensure you understand. ...
Majenko's user avatar
  • 105k
6 votes

Press the Windows key using "keyboard.press();"

They Keyboard.press() command accept modifiers per the documentation. You may need to do multiple press() commands before releasing. For example, if you want to launch File Explorer you could use: ...
Eric G's user avatar
  • 161
6 votes
Accepted

How do I prevent Arduino from running on startup?

The Leonardo should wait a couple of seconds after resetting to see if a new sketch arrives. Power off the board completely (remove the USB cable). Hold down the Reset button, and keep it held down (...
Nick Gammon's user avatar
  • 38.4k
6 votes
Accepted

Where in datasheet is the warning about unreliability of reading PINxn?

did somebody come across such case, or I'm the first in the world? You are not the first. I recently got bitten by the very same issue. However, unless you are close to an unusually strong radio ...
Edgar Bonet's user avatar
  • 43.6k
6 votes
Accepted

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/...
Craig's user avatar
  • 2,120
5 votes

Upload code on Arduino Leonardo using command line

After try some trial and error I have built a simple binary to upload into the Leonardo bootloader. This binary opens serial at 1200 baud then closes it, and wraps the avrdude binary to write .hex ...
vanbwodonk's user avatar
5 votes
Accepted

Upload code on Arduino Leonardo using command line

The problem with the Leonardo is it doesn't automatically reset when you open the serial port like boards such as the Uno do. The Arduino IDE contains code to manually reset the board (by opening the ...
Majenko's user avatar
  • 105k
5 votes

How to convert Arduino example sketch to a complete c++ project?

Basically *.ino is *.cpp without headers. So you can rename it to *.cpp, If you have any functions which are used before they have been defined, provide declarations for each function before its ...
gilhad's user avatar
  • 1,420
5 votes
Accepted

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 ...
Michel Keijzers's user avatar
5 votes
Accepted

Arduino Leonardo(Atmega32u4) - Detecting if USB is connected to a computer?

ADDEN of UDADDR is set if the '32U4 has been assigned a USB address by the host and the firmware wants to enable USB connectivity. UDADDR & _BV(ADDEN)
Ignacio Vazquez-Abrams's user avatar
5 votes
Accepted

Help with AlphaNumeric array

All of those "A1" "A2" pins have other numbers that go with them. The A1 or A2 is #defined in the core to be some number. You can just use A1 or A2 and it will work. For example, try this line and ...
Delta_G's user avatar
  • 3,378
5 votes

Generated frequency is not as expected

digitalWrite() takes a few microseconds to execute as well. There is also some overhead around the delayMicroseconds() function. If you need exactly 500 kHz, you would want to consider using a timer. ...
towe's user avatar
  • 865
4 votes
Accepted

Powering ESP8266 from Leonardo's 3.3v pin

The Leonardo is specified to provide only 50mA on the 3V3 pin. A ESP8266 can use up to almost 300mA when transmitting. Consider using a LDO regulator connected to the 5V pin instead.
Ignacio Vazquez-Abrams's user avatar
4 votes
Accepted

Can Arduino Leonardo use USB port and RX TX serial pins at the same time?

32u4 is multi-serial uC. USB connection works on default serial communication which can be used via Serial.print("somevalue"). On the other hand if you want to use RX/TX on pins 0, 1 which are ...
Sener's user avatar
  • 394
4 votes

Arduino I2C Wire.onReceive hangs after a few loops

After a bit of tinkering, I noticed that removing the delay() call in the slave fixed it and there were no more hangs. Also, when using the Servo library to move a servo instead of blinking the led, ...
Valentin Brasso's user avatar
4 votes
Accepted

Arduino Leonardo/Pro Micro sleep and USB

The Arduino has several sleep modes. They differ mainly by the clocks that are kept running, the peripherals that are enabled, and the possible wake-up sources. All these modes are described in the ...
Edgar Bonet's user avatar
  • 43.6k
3 votes

Send Keyboard Media Keys with Keyboard Library

It is indeed possible and also without the requirement to modify the Arduino environment itself. Just register an HID descriptor for the "report ID" for "Consumer Control" (the ...
Peter Mortensen's user avatar
3 votes
Accepted

What's Leonardo 5V pin current limit?

The 5V pin is either supplied by the USB port, which has a limit of 500mA (imposed by a resettable fuse) if directly connected to the computer or a powered hub (or 100mA in an unpowered hub), or the ...
Majenko's user avatar
  • 105k
3 votes
Accepted

Arduino Leonardo - Using ICSP pins for serial

From packages/arduino/hardware/avr/1.6.*/variants/leonardo/pins_arduino.h: // Map SPI port to 'new' pins D14..D17 #define PIN_SPI_SS (17) #define PIN_SPI_MOSI (16) #define PIN_SPI_MISO (14) #...
Ignacio Vazquez-Abrams's user avatar
3 votes
Accepted

why leonardo bootloader is bigger than UNO?

Apparently leonardo and UNO are very similar boards. No, they are very, very different. The Uno uses an external USB-UART bridge. This means that the bootloader code only has to read from the UART ...
Ignacio Vazquez-Abrams's user avatar
3 votes

Arduino analog input protection

If you amplified with an op-amp powered by 5V then it couldn't produce more than 5V output, so that could be your solution. Failing that, I think a resistor and a couple of clamping diodes would help. ...
Nick Gammon's user avatar
  • 38.4k
3 votes
Accepted

Getting a fixed sampling rate

You can speed your code up slightly by sending a raw microseconds reading, rather than divided by 1000000. Floating arithmetic on typical Arduino devices can be quite slow. Also, the time to ...
James Waldby - jwpat7's user avatar
3 votes

Library to set internal analog gain of the Arduino?

I would recommend you to check Nick Gammon's example on using the analog comparator by means of configuring the relevant flag bits of registers in the ATmega328. Sample code from the link, by Nick: ...
Enric Blanco's user avatar
  • 2,114
3 votes

Pressing reset button restarts program only seconds latter

The first thing that happens when you apply power to a board or press reset, is the bootloader executes. That waits for a short time to accept a new sketch over the serial port. If nothing arrives it ...
Majenko's user avatar
  • 105k
3 votes

Multiple SPI device

Some card reaaders (as well as display boards with built-in sd socket) use 10-kOhm resistors in series to the CS, DIN and CLK lines, to perform a cheap 5V to 3.3V level translation. This is really not ...
next-hack's user avatar
  • 401
3 votes
Accepted

Arduino Leonardo RX TX mystery

An Arduino Leonardo has native USB support. Which means that it has separate serial interfaces to the PC and to the hardware pins. Serial is only used for the communication with the PC and is ...
gre_gor's user avatar
  • 1,682
3 votes
Accepted

Failed to initialise SD card on Leonardo

A Leonardo has the SPI pins on the ICSP header, not on pins 11, 12, 13. And a Pro Micro has the SPI pins on 14, 15, 16.
gre_gor's user avatar
  • 1,682
3 votes

Where in datasheet is the warning about unreliability of reading PINxn?

A test with an Arduino Uno. I used the usb connector to power-on the arduino uno. The led is at PB5, so I have exchanged PB0 and PB5. My test is therefor not the same. #define LED_PB PB5 // pin ...
Jot's user avatar
  • 3,246
3 votes

Multiple Time-Sensitive Tasks

Two possible solutions: Split the serial string in small pieces so it's (comfortably) less than 50 ms and send the string in 'pieces' … you could even send it until e.g. 45 ms has been reached and ...
Michel Keijzers's user avatar
3 votes
Accepted

Why can the Xbox360 not detect the Arduino Leonardo as keyboard?

Like Juraj and Majenko said. Arduino Keyboard library does emulate "Boot Keyboard". I use NicoHood HID library and now it works.
eolandro's user avatar
  • 141

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