Wemos D1 Mini Lite can't find DS18B20
Posted: Sun Mar 11, 2018 4:26 pmBanged my head against this problem for a good 6+ hours yesterday. Hoping I could get a pair of more knowledgeable eyes on this too 
I'm trying to read data from a waterproof DS18B20 temperature sensor with a Wemos D1 Mini Lite. Here's a picture of my setup https://imgur.com/eHXnFes.
I'm using the Arduino IDE with "WEMOS D1 mini Lite" selected for my board. I followed the git installation instructions on this page https://wiki.wemos.cc/tutorials:get_sta ... in_arduino. I tried reading from the sensor and I always get the value -127. I read a suggestion to test using the DS18x20_Temperature sample script, so I did that and it prints "No more addresses." to Serial in a loop. It looks like OneWire.search(addr) is unable to find anything. Here's the sample code I'm running:
I was able to upload the example "Blink" program to the D1 mini Lite, and I was able to read good temperature values from the same sensor using a Raspberry Pi (using red/blue/yellow as vcc/gnd/data), so I don't either piece of equipment is broken.
I also read a suggestion to use a 2.2K pullup resistor instead of the standard 4.7K, but that didn't help either.
I've also tried using pins D1 and D4 instead of D2 to no avail. For what it's worth, a digitalRead of D2 always returns 0 for me.
I'm so stumped. I might just buy a normal Wemos D1 mini instead of the lite to see if that fixes it somehow. Any advice/comments would be greatly appreciated.
I'm trying to read data from a waterproof DS18B20 temperature sensor with a Wemos D1 Mini Lite. Here's a picture of my setup https://imgur.com/eHXnFes.
I'm using the Arduino IDE with "WEMOS D1 mini Lite" selected for my board. I followed the git installation instructions on this page https://wiki.wemos.cc/tutorials:get_sta ... in_arduino. I tried reading from the sensor and I always get the value -127. I read a suggestion to test using the DS18x20_Temperature sample script, so I did that and it prints "No more addresses." to Serial in a loop. It looks like OneWire.search(addr) is unable to find anything. Here's the sample code I'm running:
Code: Select all
#include <OneWire.h>
// OneWire DS18S20, DS18B20, DS1822 Temperature Example
//
// http://www.pjrc.com/teensy/td_libs_OneWire.html
//
// The DallasTemperature library can do all this work for you!
// http://milesburton.com/Dallas_Temperature_Control_Library
OneWire ds(D2); // on pin 4 (a 4.7K resistor is necessary)
void setup(void) {
Serial.begin(9600);
}
void loop(void) {
byte i;
byte present = 0;
byte type_s;
byte data[12];
byte addr[8];
float celsius, fahrenheit;
if ( !ds.search(addr)) {
Serial.println("No more addresses.");
Serial.println();
ds.reset_search();
delay(250);
return;
}
Serial.print("ROM =");
for( i = 0; i < 8; i++) {
Serial.write(' ');
Serial.print(addr[i], HEX);
}
if (OneWire::crc8(addr, 7) != addr[7]) {
Serial.println("CRC is not valid!");
return;
}
Serial.println();
// the first ROM byte indicates which chip
switch (addr[0]) {
case 0x10:
Serial.println(" Chip = DS18S20"); // or old DS1820
type_s = 1;
break;
case 0x28:
Serial.println(" Chip = DS18B20");
type_s = 0;
break;
case 0x22:
Serial.println(" Chip = DS1822");
type_s = 0;
break;
default:
Serial.println("Device is not a DS18x20 family device.");
return;
}
ds.reset();
ds.select(addr);
ds.write(0x44, 1); // start conversion, with parasite power on at the end
delay(1000); // maybe 750ms is enough, maybe not
// we might do a ds.depower() here, but the reset will take care of it.
present = ds.reset();
ds.select(addr);
ds.write(0xBE); // Read Scratchpad
Serial.print(" Data = ");
Serial.print(present, HEX);
Serial.print(" ");
for ( i = 0; i < 9; i++) { // we need 9 bytes
data[i] = ds.read();
Serial.print(data[i], HEX);
Serial.print(" ");
}
Serial.print(" CRC=");
Serial.print(OneWire::crc8(data, 8), HEX);
Serial.println();
// Convert the data to actual temperature
// because the result is a 16 bit signed integer, it should
// be stored to an "int16_t" type, which is always 16 bits
// even when compiled on a 32 bit processor.
int16_t raw = (data[1] << 8) | data[0];
if (type_s) {
raw = raw << 3; // 9 bit resolution default
if (data[7] == 0x10) {
// "count remain" gives full 12 bit resolution
raw = (raw & 0xFFF0) + 12 - data[6];
}
} else {
byte cfg = (data[4] & 0x60);
// at lower res, the low bits are undefined, so let's zero them
if (cfg == 0x00) raw = raw & ~7; // 9 bit resolution, 93.75 ms
else if (cfg == 0x20) raw = raw & ~3; // 10 bit res, 187.5 ms
else if (cfg == 0x40) raw = raw & ~1; // 11 bit res, 375 ms
//// default is 12 bit resolution, 750 ms conversion time
}
celsius = (float)raw / 16.0;
fahrenheit = celsius * 1.8 + 32.0;
Serial.print(" Temperature = ");
Serial.print(celsius);
Serial.print(" Celsius, ");
Serial.print(fahrenheit);
Serial.println(" Fahrenheit");
}
I was able to upload the example "Blink" program to the D1 mini Lite, and I was able to read good temperature values from the same sensor using a Raspberry Pi (using red/blue/yellow as vcc/gnd/data), so I don't either piece of equipment is broken.
I also read a suggestion to use a 2.2K pullup resistor instead of the standard 4.7K, but that didn't help either.
I've also tried using pins D1 and D4 instead of D2 to no avail. For what it's worth, a digitalRead of D2 always returns 0 for me.
I'm so stumped. I might just buy a normal Wemos D1 mini instead of the lite to see if that fixes it somehow. Any advice/comments would be greatly appreciated.