I didn't see anything on this in the forum. The T4 seems to not work correctly with the DS18B20 even though the Teensy 2.0 and Teensy LC do. There is a mention in the T4 beta thread that it works so maybe I'm doing something wrong. I did try it on 2 different T4s - both of which run several other large programs correctly. And, I tried several different pins for the sensor with no success.
The same sketches work on a TLC or T2.0 but not on a T4. See the first sketch for a simple program that demos the problem. The second sketch shows the 1 Wire library finding the DS18B20 on the T4 - reads the signature and correctly IDs it as a DS18B20 - but fails to read the temperature correctly. It looks like it fails to correctly read the scratchpad memory that contains the temperature data.
Neither program is mine. First one is unattributed - found it at https://create.arduino.cc/projecthu...digital-temperature-sensor-and-arduino-9cc806. There are very similar versions all over the internet - I suspect it originated at Dallas Semi. The second one is similarly unattributed.
The hardware used is very simple - DS18B20, 4.7K resistor and a Teensy. Connection is basically from the DS18B20 datasheet, page 7, figure 7. Vdd pin to 5V or 3.3V depending on processor, Gnd connected to Gnd and DQ (yes, that's what the datasheet calls the sensor pin) pulled up to Vdd via a 4.7K resistor and connected to pin 2 or 10 depending on which code.
The same sketches work on a TLC or T2.0 but not on a T4. See the first sketch for a simple program that demos the problem. The second sketch shows the 1 Wire library finding the DS18B20 on the T4 - reads the signature and correctly IDs it as a DS18B20 - but fails to read the temperature correctly. It looks like it fails to correctly read the scratchpad memory that contains the temperature data.
Neither program is mine. First one is unattributed - found it at https://create.arduino.cc/projecthu...digital-temperature-sensor-and-arduino-9cc806. There are very similar versions all over the internet - I suspect it originated at Dallas Semi. The second one is similarly unattributed.
The hardware used is very simple - DS18B20, 4.7K resistor and a Teensy. Connection is basically from the DS18B20 datasheet, page 7, figure 7. Vdd pin to 5V or 3.3V depending on processor, Gnd connected to Gnd and DQ (yes, that's what the datasheet calls the sensor pin) pulled up to Vdd via a 4.7K resistor and connected to pin 2 or 10 depending on which code.
Code:
/********************************************************************/
// First we include the libraries
#include <OneWire.h>
#include <DallasTemperature.h>
/********************************************************************/
// Data wire is plugged into pin 2 on the Arduino
#define ONE_WIRE_BUS 2
/********************************************************************/
// Setup a oneWire instance to communicate with any OneWire devices
// (not just Maxim/Dallas temperature ICs)
OneWire oneWire(ONE_WIRE_BUS);
/********************************************************************/
// Pass our oneWire reference to Dallas Temperature.
DallasTemperature sensors(&oneWire);
/********************************************************************/
void setup(void)
{
// start serial port
Serial.begin(9600);
Serial.println("Dallas Temperature IC Control Library Demo");
// Start up the library
sensors.begin();
}
void loop(void)
{
// call sensors.requestTemperatures() to issue a global temperature
// request to all devices on the bus
/********************************************************************/
Serial.print(" Requesting temperatures...");
sensors.requestTemperatures(); // Send the command to get temperature readings
Serial.println("DONE");
/********************************************************************/
Serial.print("Temperature is: ");
Serial.print(sensors.getTempCByIndex(0)); // Why "byIndex"?
// You can have more than one DS18B20 on the same bus.
// 0 refers to the first IC on the wire
delay(1000);
}
Code:
#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(10); // on pin 10 (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");
while(!Serial.available());
while(Serial.available())Serial.read();
}