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I'm actually trying to connect a DS18B20 sensor to a homemade board build with a ATmega328P processor running with a power of 3.3V and at 8 Mhz.

In order to get the address I wired the board as the following schematic on the pin 5 of my board. wire diagram (edited)

To power the sensor and the pull up resistor I use the VDD output of my board which provides 3.3V.

For the code part I uploaded this:

// This sketch looks for 1-wire devices and
// prints their addresses (serial number) to
// the UART, in a format that is useful in Arduino sketches
// Tutorial: 
// http://www.hacktronics.com/Tutorials/arduino-1-wire-address-finder.html

#include <OneWire.h>

OneWire  ds(5);  // Connect your 1-wire device to pin 5

void setup(void) {
  Serial.begin(9600);
  discoverOneWireDevices();
}

void discoverOneWireDevices(void) {
  byte i;
  byte present = 0;
  byte data[12];
  byte addr[8];

  Serial.print("Looking for 1-Wire devices...\n\r");
  while(ds.search(addr)) {
    Serial.print("\n\rFound \'1-Wire\' device with address:\n\r");
    for( i = 0; i < 8; i++) {
      Serial.print("0x");
      if (addr[i] < 16) {
        Serial.print('0');
      }
      Serial.print(addr[i], HEX);
      if (i < 7) {
        Serial.print(", ");
      }
    }
    if ( OneWire::crc8( addr, 7) != addr[7]) {
        Serial.print("CRC is not valid!\n");
        return;
    }
  }
  Serial.print("\n\r\n\rThat's it.\r\n");
  ds.reset_search();
  return;
}

void loop(void) {
  // nothing to see here
}


When I make it run on an Arduino Uno card I can get the address of the sensor but when I make it run on my card I only obtain this:

Looking for 1-Wire devices...

That's it.

Anyone got a idea why it's working on an Arduino Uno but not on my card?

hardware schematic

  • On schematic two pins are connected, in question description and code, there's only one pin. – domen Apr 30 at 10:45
  • Is that a mosfet? Is it used to shortcut the data to 3.3v? why? – Jot Apr 30 at 12:33
  • Sorry @domen i had put the wrong diagram in my post, i edited my post – Maxence Ginet Apr 30 at 14:36
  • You're saying it's same chip (and similar surrounding hardware) and same software? Is there a schematic for your own hardware, because you've probably made some mistake there. Include the details of all differences to working setup. – domen Apr 30 at 15:19
  • @domen i added in the post a hardware shematic around the chip , we use the PD5 (D5 ) – Maxence Ginet May 2 at 7:09
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I finally made it work, thx @domen.

I looked at the other part of the schematic and found I was using the wrong pin - I have two LDO and the one I was using was deactivated for sensor.

Thanks all for your help.

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