uda1321 NXP Semiconductors, uda1321 Datasheet - Page 13

• Manufacturer Part Number: uda1321
• Description: Universal Serial Bus Usb Digital-to-analog Converter Dac
• Manufacturer: NXP Semiconductors

Philips Semiconductors
responds with the appropriate settings via the audio device
class for the audio related parts or via the HID class for the
HID related inputs and outputs of the UDA1321.
A HID descriptor is necessary to inform the host about the
conception of the user interface. The host communicates
via the HID device driver using either the control pipe or
the interrupt pipe. The UDA1321 uses USB endpoint 0
(control pipe) to respond to the HID specific ‘Get/set report
request’ to receive or transmit data from or to the
UDA1321. The UDA1321 uses the status interrupt
endpoint as interrupt pipe for polling asynchronous data.
The UDA1321 is a high-speed device. The maximum
transaction size is 64 bytes per USB frame and the polling
rate is defined at a maximum of every 1 ms.
The host requests the configuration descriptor which
includes the standard interface descriptor, the HID
endpoint descriptor and the HID descriptor. The HID
device driver of the host then requests the report
descriptor.
Report descriptors are composed of pieces of information
about the device. Each piece of information is called an
item. All items have a 1-byte prefix that contains the item
tag, type and size. In the UDA1321 only the short item
basic type is used.
The hosts HID device driver will parse the report descriptor
and the defined items. By examining all of these items, the
HID class driver is able to determine the size and
composition of data reports from the device.
The main items of the UDA1321 are input and output
reports. Input reports are sent via the interrupt pipe
(UDA1321 USB address 3). Input and output reports can
be requested by the host via the control endpoint (USB
address 0).
The UDA1321 supports a maximum of three pushbuttons,
which represents a certain feature of the UDA1321. If
pressed by the user the pushbutton will go to its ‘ON’ state,
if not pressed the pushbutton will go back to its ‘OFF’ state.
The UDA1321 supports a maximum of two outputs for e.g.
user LEDs.
For more information about the input and output functions
of the UDA1321 see the application documentation of the
device.
1998 Oct 06
Universal Serial Bus (USB)
Digital-to-Analog Converter (DAC)
13
Controlling the USB Digital-to-Analog Converter
(DAC)
This section describes the functionality of the feature unit
of the UDA1321. The mapping of this functionality onto
USB descriptors is as implemented in the firmware.
The sound features as defined in the “USB Device Class
Definition for Audio Devices” are mapped on the UDA1321
specific feature registers by the microcontroller. These
specific sound features are:
These specific features can be activated via the host
(audio device class requests) or via the GP pins (HID plus
audio device class requests). Via the I
able to download the necessary configuration data for
different applications (definition of the function of the GP
pins, with or without digital I/O functionality, etc.).
The mapping and control of the standard USB audio
features and UDA1321 specific features is described
below.
V
Volume control is possible via the host or via predefined
GP pins. The setting of 0 dB is always referenced to the
maximum available volume setting. Table 3 gives the
mapping of wVolume value (as defined in the “USB
Device Class Definition for Audio Devices” ) upon the
actual volume setting of the USB DAC. When using the
UDA1321, the range is 0 down to 60 dB (in steps of 1 dB)
and
possible. It should be noted that wVolume bits B7 to B0
are not used. Values above 0 dB are returned as 0 dB.
The volume value at start-up of the device is defined in the
selected configuration map.
Balance control is possible via the separate volume control
option of both channels. Therefore the characteristics of
the balance control are equal to the volume control
characteristics.
OLUME CONTROL
Volume control (separate for left and right stereo
channels, no master channel)
Mute control (only master channel)
Treble control (only master channel)
Bass control (only master channel)
Dynamic bass boost control (only master channel).
dB. Independant control of ‘left’/’right’ volume is
Preliminary specification
2
C-bus the user is
UDA1321