7
The problem is that float numbers are seldom an exact representation. So the float is stored as the closest number that is exactly representable as a float, namely
10446438 × 2−18 = 39.84999847412109375.
When you multiply this by 100, you get 16322559 × 2−12 = 3984.999755859375.
And than casting to an int or long results in 3984, not 3985.
so whenever you ...
4
This manual page of strlcpy() is quite clear:
If the src and dst strings overlap, the behavior is undefined.
This means you should avoid it, even if it works on some tests. The
advice you got of just trying is not good advice. Use
memmove() instead.
3
analogRead() returns 0x0000 to 0x03ff
If the max data 0x03ff is shifted to the right by 3 bits (or divide by 8),
then 0x03ff becomes 0x007f, or 127.
I think this will do it:
desiredMax = analogRead(A0) >> 3; // divide 1023 max by 8, becomes 127 max
3
You can connect via:
UART
I2C
SPI
All are available on the Pi's GPIO header and on the Arduino. You will of course need logic level translation for a 5V Arduino.
Using UART is probably simplest for you since that is identical to using the USB - you just use /dev/ttyS0 (or /dev/ttyAMA0 on older Raspberries) instead of /dev/ttyUSB0 or /dev/ttyACM0. Just ...
3
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 continue in the next round. Use the Blink Without Delay mechanism to switch between the tasks.
More robust solution: Make Task 2 an interrupt... This is probably ...
2
(Answering in more detail, as this is the top search hit for "ESP8266 Vin", at least for me)
TL;DR: Vin is NOT directly connected to USB power. There is a protection diode between USB+/VU and Vin, which has a limited current capacity.
If your board provides VU, that one is directly connected to USB power.
As long as you only power 1-2 tiny devices, it ...
2
Here lies your ≈ ½ ms problem:
#include <SoftwareSerial.h>
SoftwareSerial is very time sensitive. It generates the serial stream by
bit-banging, with interrupts disabled. For each byte sent, interrupts
are disabled just before sending the start bit, and re-enabled just
after the stop bit has been written. At 9600 bps, interrupts are
thus ...
2
You can use the map function, see https://www.arduino.cc/reference/en/language/functions/math/map/.
Example: If your pot meter gives values from 100 to 1000 and you want to map that range to a range of 0 to 128 you can easily write:
potValue = map(readValue, 100, 1000, 0, 128);
High likely, in your case and if the potentiometer is 'perfect' it returns ...
1
In this line:
SCENARIO btns[4] = { _red, _yellow, _white, _stop};
you are making 4 copies of the structures and placing them in an array.
Instead you should either create the array directly with the values:
SCENARIO btns[4] = {
{-1, -1},
{-1, -1},
{-1, -1},
{8, 4}
};
And only use the array, or use pointers in the array:
SCENARIO *btns[...
1
The problem is that a struct is handled as a value type, not as a reference type.
This means that a copy of _stop is made and put in btns (btns[3] actually).
So what you need to do is putting pointers into the btns array:
SCENARIO* btns[4] = { &_red, &_yellow, &_white, &_stop};
The symbol * denotes a pointer, and & means the address ...
1
"Pseudo-code" isn't a programming language. It is just a term that we use when we write code that looks like code but can't be compiled, because it's half-English, half-code. You write pseudo code when you want to communicate to another human how code is supposed to work without getting bogged down in the details.
1
Because you're using delay() within your while loop you have to ensure that you are pressing the key at the precise moment it is read.
You should not use delay().
Instead take a look at the BlinkWithoutDelay example in the IDE. And also consider implementing a Finite State Machine to know both if you're blinking and what state you're blinking currently is ...
1
Acceleration is a vector quantity. Therefore, instead of looking at the average values of X,Y, and Z, you should probably look at the magnitude of the acceleration vector, that is (X^2+Y^2+Z^2)^0.5. Then, you can set an acceleration threshold below which you would send no data.
The benefit of using the magnitude of the acceleration vector is that it is ...
1
You can use the millis function to check the current 'time'. If you store this, and later call this function again, by subtracting you can see how much time has been passed. so instead of delay(500) you use if (millis() - timeStamp >= 500) { ... to continue your code.
As others said in comments, you also need to debounce to prevent multiple button ...
1
CS12 has a value of 2 since it represents bit 2 of the TCCR1B register.
(1 << CS12) takes the value 1 (0b00000001) and shifts it left 2 times to get (0b00000100).
The order of operations dictates that things in () happen first, so this is done before the "|=" is evaluated.
(1 << CS10) takes the value 1 (0b00000001) and shifts it left 0 times ...
1
You cannot pass an array of characters as an argument (implicit or not)
to a function. When you write
String rtcTimeString(char ts[] = "MM/DD/YY hh:mm:ss");
The array notation is implicitly converted to a pointer. The line above
is then equivalent to:
String rtcTimeString(char *ts = "MM/DD/YY hh:mm:ss");
And this is incorrect: you are initializing a ...
1
This basic C++ (and GIYF).
What about
String Esper::rtcTimeString(std::string dateTimeForamt = "MM/DD/YY hh:mm:ss")
{
DateTime now = rtc.now();
return now.toString(dateTimeForamt );
}
See, for instance, this question. Hope this helps :-)
1
There are two issues at play here:
1 – Limited precision of the float data type
A float has a precision of roughly 10−7, and any number that
is not an exact float is supposed to be rounded to the nearest float.
For example, the two floats closest to 1.234567 are
10356298 × 2−23 = 1.2345669269561767578125 and
10356299 × 2−23 = 1.23456704616546630859375.
The ...
1
It depends actually on your requirements what is 'best'.
If (transmission) speed is an issue, there are mainly some things you can do to improve this:
Increase the transmission speed (this depends on the distance of the wires and the noise).
Decrease the start/stop bits (this reduces the certainty the values will arrive ok)
Pack your data (takes more ...
1
Old time and new time are wrong way round on a part where the LED'd are switched off
else if(oldTime-newTime >= dt){
oldTime=newTime;
digitalWrite(led1,LOW);
}
When simple processors reach the max or min value and continue counting, they overflow and start counting from far end: So 5-8=maxint(largest number)-3
Result is that ...
1
I don't think anything in your code is going to work.
First,
you are asking the serial.Read to return an integer if it is working. You might want to change that to a Boolean.
Second,
You are asking for a 1 and only a 1 to make your next if statement true. If the serial.Read is working the chance it will only return a one, I think is very low
Third,
On ...
1
In fact all the mentioned function calls are using the Special Function Registers (SFR) and thus the hardware peripherals of the Arduino in the background to work. But I guess this is an exercise to learn how to configure and use these peripherals yourself. Doing this for the whole code is a rather big task for a single question on this site. So I will give ...
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