How do I handle an array of bytes easily?

Projects Programming
1

I want to handle 10 temperature sensors (type DS18B20). Therefore I initially read all addresses of the sensors. Each address consists of 8 bytes. I can successfully read all addresses of all sensors. One address can be stored in a byte-array, i.e.:

byte SensorAddr[8];

For easy handling in different functions I would like to store all available sensor-addresses in an array, i.e.:

uint8_t AllSensorsAddr[10][8];

My question:
How can I store all 8 bytes at one time in the array?
Something like

  while(DS1820.search(SensorAddr)) {
    if ((SensorAddr[0] == 0x10) or (SensorAddr[0] == 0x22) or (SensorAddr[0] == 0x28)) {
      AllSensorsAddr[SensorCtr] = SensorAddr;
      showAddress(SensorCtr, SensorAddr);
      SensorCtr++;
    }
  }

The compiler says:

error: invalid array assignment
       AllSensorsAddr[SensorCtr] = SensorAddr;
                                 ^

Thanks for helpful hints.

2

There are no compound assignments of base types in C++. You are trying to copy a vector of values with one assignment statement (because one dimension of a 2 dimensional array is itself an array, not a single value).

You have to copy the values one by one, or use some function that does that. You could create a Sensor Address class, and overload the '=' operator to perform that function.

3

Maybe this is a case for memcpy() ?

...R

4

"Easy handling" of arrays by different functions is usually done by somehow managing to keep the data in one place and pass pointers to the data to those functions, instead. I don't know enough about your program to suggest how you might do that.

5

aarg:
There are no compound assignments of base types in C++. You are trying to copy a vector of values with one assignment statement (because one dimension of a 2 dimensional array is itself an array, not a single value).

Not if you use C-style arrays, but you can simply copy C++ std::arrays without any issues:

#include <array>

#include <OneWire.h>

void setup() {
  Serial.begin(115200);
  const uint8_t pin = 2;
  OneWire ow(pin);

  std::array<uint8_t, 8> address;
  std::array<std::array<uint8_t, 8>, 10> addresses;
  uint8_t count = 0;

  while (ow.search(address.data()) && count < addresses.size()) {
    addresses[count] = address;
    count++;
  }
}

This won't work on AVR Arduinos, because they don't ship with the C++ standard library out of the box. It will work on ARM boards and ESP32/8266 boards.

That being said, it's much easier to just store the addresses in your array directly:

 constexpr uint8_t num_addresses = 10;
  uint8_t addresses[num_addresses][8];
  uint8_t count = 0;

  const uint8_t pin = 2;
  OneWire ow(pin);
  while (count < num_addresses && ow.search(addresses[count])) {
    count++;
  }

aarg:
You have to copy the values one by one, or use some function that does that. You could create a Sensor Address class, and overload the '=' operator to perform that function.

There's no need to overload the assignment operator, the default one that's generated by the compiler will do a deep copy of the array members for you.

Pieter

6

Thanks @aarg and @Robin2 for the different hints and tipps. I will have a more close look to the mentioned methods in order to learn more about c++

For my sensor-task I have choosen the method from @PieterP to directly assign the address in the read-command.

while (count < num_addresses && ow.search(addresses[count])) {
count++;
}
There's no need to overload the assignment operator, the default one that's generated by the compiler will do a deep copy of the array members for you.

Pieter

In my opinion it´s the most direct way to solve the issue.

Thanks to all of you!