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UHD - Coding to the API
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.. contents:: Table of Contents

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Low-Level: The device API
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A device is an abstraction for hardware that is connected to the host system.
For a USRP, this means that the motherboard and everything on it would be considered to be a "device".
The device API provides ways to:

* Discover devices that are physical connected to the host system.
* Create a device object for a particular physical device identified by address.
* Register a device driver into the discovery and factory sub-system.
* Streaming samples with metadata into and out of the device.
* Set and get properties on the device object.

See the documentation in device.hpp for reference.

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High-Level: The simple usrp
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The goal of the simple usrp is to wrap high level functions around the device properties.
The simple usrp provides a fat interface to access the most common properties.
The simple usrp provides ways to:

* Set and get daughterboard gains.
* Set and get daughterboard antennas.
* Set and get the streaming rates.
* Tune the DSPs and daughterboards.
* Issue stream commands.
* Set the clock configuration.
* Set the usrp time registers.
* Get the underlying device (as discussed above).

It is recommended that users code to the simple_usrp api when possible.
See the documentation in usrp/simple_usrp.hpp for reference.

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Integrating custom hardware
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Creators of custom hardware can create drivers that use the UHD API.
These drivers can be built as dynamically lodable modules that the UHD will load at runtime.
For a module to be loaded at runtime, it must be found in the UHD_MODULE_PATH environment variable.

^^^^^^^^^^^^^^^^^^^^^^^^^^^
Custom motherboard
^^^^^^^^^^^^^^^^^^^^^^^^^^^
Create a new device driver when the driver in lib/usrp/
cannot support your custom FPGA or hardware modifications.
Make a copy of the relevant driver code in lib/usrp/, make mods, and rename the class.
The new device code should register itself into the discovery and factory system. 

^^^^^^^^^^^^^^^^^^^^^^^^^^^
Custom daughterboard
^^^^^^^^^^^^^^^^^^^^^^^^^^^
Use code from an existing daughterboard in lib/usrp/dboard/* as an example.
Your daughterboard code should subclass an rx dboard, rx dboard, or xcvr dboard;
and it should respond to calls to get and set properties.
The new daughterboard code should register itself into the dboard manager
with a unique rx and/or tx 16 bit identification number.