5
votes
Accepted
Digital I/O threshold voltages for ATmega32u4
LVTTL is Low Voltage Transistor-Transistor Logic. In general, the
term "TTL" is used for a digital signal.
The "Low Voltage" part is special,
the ATmega32U4 switches from low to high (and vice versa) ...
- 3,286
5
votes
Accepted
How to set sampling rate for digital pin input?
You need:
A timer
A board that is capable of running fast enough to do what you want.
The Nano fits the first criteria, but not the second.
At 16MHz you get a clock period of 63ns. That means you ...
- 106k
4
votes
USB reset fails on arduino due because of 5v on digital pins
You're over-stressing the MCU and causing all sorts of horrible things to happen with the power rails. Of course nasty things are going to happen.
The only way to fix it is to change the circuitry. ...
- 106k
4
votes
Accepted
Digital Pins reads 1 when configured with internal_pullup
There is no difference between a switch and a "pin" for input. All are either HIGH or LOW. You tie it HIGH with the pullup, and then try giving it a HIGH with +5V (Caution: The Due is a 3.3V device, ...
- 106k
3
votes
Accepted
How much voltage and current can a Arduino uno digital input sink?
One common misconceptions is that the current limit of a GPIO pin applies to inputs. It does not.
The 40mA "maximum sink" is only applicable when the pin is set to OUTPUT and is driven LOW - at ...
- 106k
3
votes
Cannot read LED state
A digital input on the Arduino Uno is guaranteed to read LOW if the
input voltage is less than 1.5 V. It is guaranteed to read HIGH
if that voltage is above 3.0 V. For any voltage in between, you
have ...
- 45.2k
3
votes
How to set sampling rate for digital pin input?
Note: this is an attempt to answer the question as asked. This
answer is unlikely to be of any use to the original poster, who
presumably asked the wrong question. I am writing this only as a way to
...
- 45.2k
3
votes
Accepted
Fast digital IO
You can do this with an Uno, provided it has nothing else to do. I would
program it low-level, skipping the Arduino core since, as you said,
digitalWrite() would be too slow for this application.
Here ...
- 45.2k
2
votes
Accepted
Cannot read LED state
For the CMOS logic the treshold is usually 1/2 Vcc, therefore you might get lucky with arduino 3.3V Arduinos, but it's still in undefined area. That usual threshold can also change with operating ...
- 4,907
2
votes
Reading multiple DI pins in parallel as one byte/word
I'm sure time has already passed for this persons project. But for those visiting this page for whatever reason (mine was different than the information here) here is a solution I would implement. ...
- 21
2
votes
Accepted
Additional Digital Input Pins
You could use a GPIO expander (MCP23017 or similar) which could give you 14 extra pins (16-2 for I2C bus), but this is putting extra load on the microprocessor. (you haven't said which one by the way)...
- 5,652
2
votes
Accepted
Mixing analog reads with raw port reads
What you are trying to do is perfectly safe. In fact, you reading PINC
will have no effect whatsoever on the input circuitry. You are just
reading an I/O register and, whether you read it or not, this ...
- 45.2k
2
votes
Accepted
Read Digital Input from Arduino Pin defined as OUTPUT
If you want to know the state of the load, I suggest to put the
mechanical switch on the low-voltage side of the relay:
simulate this circuit – Schematic created using CircuitLab
The voltage ...
- 45.2k
2
votes
arduino mega buzzer output
Any time you have the same sequence of code repeated over and over with slight variations, that is a "code smell" (an indication that you may be using the wrong approach.)
You should use ...
- 5,752
1
vote
How long does my digital pulse need to be for it to be read?
As explained by Majenko's answer, you should detect the pulses from an
interrupt and print the result from the regular code. However, instead
of just setting a flag in the interrupt handler, I suggest ...
- 45.2k
1
vote
How long does my digital pulse need to be for it to be read?
This is exactly the reason interrupts were invented. They can respond a lot faster than a simple digital read. By "a lot" I mean orders of magnitude.
When an interrupt is triggered your interrupt ...
- 106k
1
vote
How can I scan for a HIGH signal on digitalRead during the main loop, while running other things?
Simplify, and show your setup code.
First, do you have a pinMode call in your setup function:
void setup() {
pinMode(A15, INPUT_PULLUP);
Serial.begin(115200);
}
Then use test code like this:
...
- 5,752
1
vote
Accepted
Using NodeMCU D8 (GPIO15), D4 (GPIO2) and D3 (GPIO0) pins
The boot setup pins have pull-up on board (0, 2) and pull-down (15) to ensure the correct boot. io 0 (D3) is additionally wired to the reset circuit controlled over USB to put the esp8266 into ...
- 18.3k
1
vote
How to monitor state of 50 Digital Inputs
I had a project that used 16 rotary encoders and I used the MUX Shield which uses 74HC4067 analog multiplexers. They port to A0 - A3 on the shield which is fine as you can set these pins to Digital ...
- 112
1
vote
Mixing analog reads with raw port reads
In general, most embedded processors multiplex external pins into specialized internal circuits. Circuits which check standard fixed threshold crossings (digital inputs), circuits which check ...
- 7,513
1
vote
Accepted
Reading input from digital pins 36, 37, 38 in Arduino Mega 2560 is giving a problem
I expect the problem is in the circuit. To be sure, put a serial print statement directly after reading the inputs, to be sure the input values are read correctly.
See the remark of using INPUT or ...
- 13k
Only top scored, non community-wiki answers of a minimum length are eligible