onewire
This class includes full support for Onewire devices using the ESP32 RMT peripheral to achieve very precise timing
1-Wire is a device communications bus system designed by Dallas Semiconductor Corp. that provides low-speed data, signaling, and power over a single conductor.
1-Wire is similar in concept to I²C, but with lower data rates and longer range. It is typically used to communicate with small inexpensive devices such as digital thermometers and weather instruments. A network of 1-Wire devices with an associated master device is called a MicroLAN.
One distinctive feature of the bus is the possibility of using only two wires: data and ground. To accomplish this, 1-Wire devices include an 800 pF capacitor to store charge, and to power the device during periods when the data line is active.
| ESP32 | Device |
|---|---|
| any ouput capable port External pull-up resistor (1K - 4.7K) to +3.3V is needed |
D (data pin) |
| GND | GND |
| +3.3V | Vdd (optional) |
The 1-wire devices can be connected in two power modes:
-
Normal power, +3.3V is connected to the device's Vdd pin
- Parasite power, device's Vdd pin is connected to the GND pin, the needed power is supplied by the data pin
- The used Power mode is detected automatically by the driver
- All devices connected to the same 1-wire bus must operate in the same mode
Normal power mode connection:
Parasite power mode connection:
ow = machine.Onewire(pin)
