5 Protocols

A protocol is needed when multiple devices communicate over the same line. The complexity of such protocols depends on multiple factors of the one-wire system:

  • The number of devices connected
  • The number of masters
  • Possibility for the devices to connect and disconnect
  • Signal integrity in the environment that the bus is operating in
  • The diversity of the clock speeds for the devices
  • Data rate

The 1-Wire protocol provides a good solution in regards to almost all of the points above, but the data transfer rate is limited. Its maximum transfer rate is 14400, and some of the bus time and data are used for protocol overhead.

Section Get Source Code from Atmel | START provides a link to a simple example showing the USART communicating at higher speeds using one-wire. The example sets one device to listen for communication and another to initiate it. The data sent between the devices is of fixed length. The device initiating the first transfer always expects to receive data in return from the other device, before sending new data.