This QuickByte shares two SPIN2 code examples that enable the P2 to communicate with 1-wire devices. We are using the common DS18B20 1-wire temperature sensor in these examples, although the driver could be extended for any 1-wire device.
1 = GND (Connect to one of the GND pins on your P2 breakout board)
2 = P2 I/O Pin (Connect to an I/O pin, P7 used in the example code)
3 = 3.3V (Connect to One of the Vxx pins on your P2 breakout board)
The two example code archives are available to download from the Source Code link below.
Open Propeller Tool and load the code example.
Tip: Unzip the example code archive and then use PropellerTool to open the main file, which in the case of these examples can be identified by the _demo tag at the end of the filename. You can always find the main file of any PropellerTool archive by consulting the “_README.txt” file inside the archive. All the source code files are listed, with the main file at the top.
In the example code files, ensure the 1-wire I/O pin matches the pin connected to your sensor. We have used pin 7 in the example, but you can change it to any spare I/O pin you prefer:
And for example 2, also ensure the serial number of the 1-wire device matches your serial number! You can read your serial number using code example 1.
Within PropellerTool:
The code will now be running in your P2, and will be waiting to receive a keypress on the serial terminal before it starts transmitting data. This allows you time to set up your serial terminal as follows:
Within the PST:
Once you press Enter, the output from the P2 program will be displayed in the terminal. This is the typical output from Example 1:
Connecting 1-wire devices to the Propeller P2 is very simple, and in most cases they do not require any additional components, such as pull-up or series resistors, as the P2 SmartPins can emulate those functions.
For help please feel free to ask your questions here, or for a wider audience of helpers at our Forums: https://forums.parallax.com.
