Detailed Features
STV0681
Table 2: List of custom sound functions
Frequency 50kHz
Frequency 60kHz
Note: 1 When a sound is associated to a given function, and it is stored in SDRAM, the piezo buzzer does
not give any beeps for that function. Not all functions need to have custom sounds associated with
them, this is the choice of the user or OEM.
2 A demonstration PC application “CustomSounds” is available from ST, however this is not intended
for end-users. Source code is available which allows the OEM to build their own PC application
using the SDK.
2.3
Battery level detect and USB auto-switch
An on-chip battery level detector on STV0681 detects when the battery voltage falls below a
threshold. The chosen threshold level is determined by a resistor value, as shown in Chapter 7.
Where no USB has been detected, the LCD display flashes, indicating that the battery is low. When
a USB connection has been detected, the LCD display does not flash.
Note: It may be a requirement of certain USB compliance tests that such additional hardware is included
in the camera design, in order to enable the camera to switch to supply from USB and hence report
back to the PC while connected to the USB bus without a battery.
2.4
Audio record and playback
2.4.1 Record
A camera including the STV0681 with a microphone, a comparator and other periphery (also using
the sensor pre-amplifier) can record sounds stored like images. STV0681 auto-detects the
presence of audio record hardware and includes audio record and “delete last” functions into the
user interface. The audio sample rate is 11.025 kHz, the signal is digitized using a successive
approximation A-D converter with 8 bits resolution. The SDRAM stores 1 second of audio recording
per 11 kByte of memory.
2.4.2 Playback
A camera including the STV0681 with an amplifier, a speaker/headphone socket and other
periphery can playback sounds either recorded on the camera or downloaded from the PC.
The quality of audio playback is largely dependant on the type of speaker used, and on the correct
mounting of the speaker in the camera plastics.
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ADCS 7283313C
STMICROELECTRONICS [ ST ]
