Thanks for all the great responses.

I actually figure it out. I knew that my sensors were working because I could get the same code to work when using a ESP8266. I'm currently using GPIO25 for my 5 DS18B20 temperature sensors and I'm also using a 4.7 Ohm resistor as suggested by Dallas. At first, I could not see any sensor. After some thinkering, I was able to get the mac addresses of all 5 sensors with the Atom Lite but the temperature was ALWAYS 85. Googling for 85, someone said that we have to wait 750 ms after calling sensors.requestTemperatures();

sensors.requestTemperatures(); delay(750); // This seems critical to get the sensors to work with AtomLite

Then I can proceed to get the temperatures like so. Note that this only illustrates the spirit of what needs to be done and I haven't tested the exact code that follows.

#include <M5Atom.h> #include <OneWire.h> #include <DallasTemperature.h> // GPIO where the DS18B20 is connected to const uint8_t oneWireBus = GPIO_NUM_25; // Setup a oneWire instance to communicate with any OneWire devices OneWire oneWire(oneWireBus); // Pass our oneWire reference to Dallas Temperature sensor DallasTemperature sensors(&oneWire); void setup() { M5.begin(true, false, true); // But I need to test without this line. sensors.begin(); } void loop() { sensors.requestTemperatures(); delay(750); // This seems critical to get the sensors to work with AtomLite const unsigned int num_DS18B20 = sensors.getDeviceCount(); for (unsigned int i=0; i<num_DS18B20; ++i) { DeviceAddress mac; sensors.getAddress(mac, i); delay(10); const float temperature = sensors.getTempCByIndex(i); send_MQTT(mac, temperature); } } delay(10000); }

I hope that this information will be useful for someone else trying to hookup some DS18B20 to an Atom Lite.