The next feature the board offers is inherent non-volatile automatic gain control. The first time a new sound
file is played by the DF Player, the Wee Little Talker board
cleverly records the highest volume points in the audio file
and — if it is not the full 255 value the ADC is capable of
recording — it will create a “scaling” factor and store it in
the EEPROM of the PICAXE. This avoids having to set the
gain to get optimum jaw deflection when using an audio
track that is recorded at middle or low volume.
Every time the sound file is played, the maximum
volume level detected during playback is stored in
EEPROM without the user having to take any steps to
cause this to happen. This is a truly automatic gain control!
So, if having computing power, an EEPROM saved
setup, LED, and servo drivers already on board weren’t
enough, the Wee Little Talker also hosts the DF Mini MP3
player board. This is a full featured MP3 player with a
built-in audio amplifier (Figure 12) and is the reason the
board can offer yet another high-tech feature: a voice-driven menu system.
What’s On the Menu?
The Wee Little Talker has an onboard voice driven
setup menu (see Resources for video demonstration).
Using just three onboard pushbuttons, the Wee Little
Talker board will verbally guide you through the entire
setup of the system — no PC or external connections
required. This is accomplished by having prerecorded
voice prompts on a micro SD card and calling them one
by one. The menu structure is shown in Figure 13.
Just by stepping through the menu, you can program
all of the features of the board. Here’s a quick overview of
the menu options:
Servo Positioning: This adjusts the servo position to
the maximum jaw open and closed positions of your
September 2017 43
■ FIGURE 13. Wee Little
Talker voice prompt
■ FLOWCHART 1.