By default, unless driven by your application as inputs or outputs, or set similarly in the fuse table, all GPIO are tristated (hi-z) at boot. You can explicitly tristate a pin and optionally drive it to the asserted (high) or de-asserted (low) state in your application.

The 02-tristate Sample Application

The application provides five CLI functions for setting the state of pin DP2 (GPIO 21):

• out <0|1> - sets the pin to be an output and sets the level to low (0) or high (1)
• tristate <0|1|2> - set the pin to tristate, with no pull-up (0), pull-up (1) or pull-down (2)

Each CLI command prints the current state of the pin:

Tristate app, ver 1.2.0.1
SmartMeshIP stack, ver 1.4.1.6

> out 1
Setting pin to output 1


> tristate 0 
Setting pin to tristate with no pull

Implementation Details

The 02-tristate sample application uses the Helper Modules to initialize the CLI Module and for interaction with the local interface. It passes JOIN_NO in the fJoin flag when initializing the local module in the loc_task_init() to prevent the local module from attempting to join. It includes five CLI handlers for setting the various pin states.  

It uses a single task (tristateTask) that:

• Opens the DP2 pin.
• Waits in a while(1) loop.

All pin setting changes are handled directly in the CLI handlers.  Since the CLI handlers block other application tasks, the CLI handlers can be written to copy information to a global variable and post a semaphore for asynchronous handling by another task.