Sensor Calibration Scan after a Button Input

Other Hardware Sensors
1

First off, massive respect to those who spent their time helping on the forums.

Personally I have learnt so much from troubleshooting using the forum search bar, a big thanks.

My problem. (I'm assuming it will be a easy fix)

I have a loadcell +amp chip, achieving good signals.

My system currently calibrates itself on start up. (I physically cycle the load cell)

[while (millis() < 5000) {
sensorValue0 = analogRead(sensorPin0);

// record the maximum sensor value
if (sensorValue0 > sensorMax0) {
sensorMax0 = sensorValue0; }

// record the minimum sensor value
if (sensorValue0 < sensorMin0) {
sensorMin0 = sensorValue0; }
]

I then map the values for the processing i require.

I do not have the experience to define a calibration sequence (for a time period, like 5 seconds) after a button demand.

I have done all the relevant tutorials but I cannot find something that works.

My button command will have to be a analog signal, just to make things a little more awkward. Eg:

[
buttonState = analogRead(A3);
if (buttonState > 1000) { Do something}

]

To summarise - How do I calibrate a sensor for a given time period after a command?

A flow chart along the lines of:

[Button Pressed] -> [Start calibration 'scan'] -> [5secs delay]-> [Stop Cal scan]->[Generate Min and Max Values]

Kind regards,
Calibration-Noob Will.

2

There are a lot possibilities. You could use a hardware timer, interrupts, interrupt service routines, etc.

But let's start to make it easy.
First of all, this code "while (millis() < 5000)" will only work if millis() starts at 0, so it is only valid at startup.
Make that code work at any moment:

unsigned long millis_now = millis();
while (millis() < (millis_now + 5000))

How do you set the initial values for sensorMax0 and sensorMin0.
You could do it like this:

// set initial values
sensorValue0 = analogRead(sensorPin0);
sensorMax0 = sensorMin0 = sensorValue0;

// Find min and max
unsigned long millis_now = millis();
while (millis() < (millis_now + 5000))
{
  ...

Next, place the calibration in a function.

int sensorMin0, sensorMax0;
void Calibrate(void)
{
  ...
}

The sensorMin0 and sensorMax0 are globally, and can be used anywhere.
If you want the function to return them, you have to use parameters with pointers to integers.

Call the function at start, en when the butten is pressed.

3

Many thanks for the reply Krodal.

"millis_now" was the command I was after! :slight_smile: (Wish i knew about it before)

I appreciate your response, I can finally finish what I was doing.

Kind regards,