Chameleon-PIC Nurve Networks, Chameleon-PIC Datasheet - Page 69

• Manufacturer Part Number: Chameleon-PIC
• Description: MCU, MPU & DSP Development Tools PIC24 & PROPELLER DEV SYSTEM (SBC)
• Manufacturer: Nurve Networks

Specifications of Chameleon-PIC

• Processor To Be Evaluated: PIC24
• Data Bus Width: 16 bit
• Interface Type: USB, VGA, PS/2, I2C, ISP, SPI
• Operating Supply Voltage: 3.3 V, 5 V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

J6
J5
J6
J6
J6
J6
J7
J7
J7
J7
J7
J7
J7
J7
Note 1: Power pins 5VCC, 33VCC, GND don’t actually connect to the PIC, but to the system power lines which in turn are
electrically connected to the PIC’s AVDD, VDD, and VSS(GND) respectively.
Note 2: VIN is connected to the 5V regulator’s input pin. This signal reflects the input analog voltage plugged into the 9V
DC power jack. If only the USB power is plugged in this signal will be floating or near ground.
14.0 Audio Hardware
There is no dedicated audio hardware inside the PIC chip nor the Propeller chip, therefore we have to rely on “software
techniques” to create sound for the system. However, knowing that software is going to be used to generate sound we
can add a little analog circuitry to “help” the audio software out and allow us to use certain common techniques for
generating sounds. The Propeller does have counters on board and can generate PWM signals, thus the audio drivers
typically leverage these hardware elements. Thus, for most audio applications that connect to a Propeller chip all you
need is a typical PWM “integrator” or “low pass” filter. The Chameleon employs such a hardware design as shown in
Figure 14.1.
Referring to the circuit, we see that the signal AUDIO_MONO (I/O P24, pin 31 on the Propeller) is an input into the
network. This signal is passed thru a low pass filter consisting of a resistor (R14 @ 1K ohm) and a capacitor (C15 @
0.1uF). Note these reference designators may change in the future, but the point is there is an R/C network here. Moving
on there is also another AC coupling capacitor (C14 @ 10uF) to the final RCA output. The circuit has two sections and
they each serve different purposes. Refer to Figure 14.1 for the following explanation.
Figure 14.1 – The analog audio hardware on the Chameleon PIC
DPIN14
DPIN8
AIN3
AIN2
AIN1
AIN0
GND
GND
RESn
33VCC
5VCC
GND
GND
VIN
2
1
1
1
1
1
1
© 2009 NURVE NETWORKS LLC “Exploring the Chameleon PIC 16-Bit”
17
18
7
26
25
3
8,19,27
8,19,27
1
13,28
NA
8,19,27
8,19,27
NA
RB8 (SDC)
RB9 (SDA)
RB3
RB15
RB14
RA1
GND
GND
nMCLR
VDD,AVDD
NA
GND
GND
NA
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