Project Check Point 3

Audio Interface

Jeff Du

Overview Project specs and overview next Tue. Mid-term next Thurs. This audio interface lab is REALLY

easy. Norm is kind enough to provide most

of the logic blocks. You just need to do some wire wrap

and control logic for A to D.

Audio Interface(high level)

FIFO

FIFO

SRAM

UARTIN

UARTOUT

Main ControlFSM

Collision

Audio Ininterface

Audio Outinterface

Packet Logic

D To A A To D

Audio Interface(this lab)

Audio InControl Logic

Audio OutControl Logic

D to A Circuits

A to D Circuits

Function Generator

Oscilloscope

Xilinx ChipXilinx Board

Analog To Digital Chipset (1) We will use the ADC08161 and a discrete

pack that contains some capacitors PIN:

Input(1), Function Gen. CS.L(13), Vref(11), GND(10) to GROUND, (6, 7, 9, 18) unused, (12, 19, 20) to the discrete pack, DataOut(2-5, 14-17) connect to the SRAM. (Look at www.national.com/ds/AD/ADC08161.pdf P14)

RD.L (read input), pin 8, should be controlled the xilinx chip.

You need to connect DataOut to the DataIn for the SRAM, D0 to D0, D1 to D1, ……….

Analog To Digital Chipset (2) RD.L should be low for 200ns – 400

ns for a correct conversion. Since we are using 8 KHz clock(each

cycle is 125ns), we should delay the RD.L signal for 2-3 cycles.

For details, read page 12 section 2.2 on the spec.

ADC generates 16 bit unsigned number!

Function Generator Connect the ground to the borad Connect the signal to the input

pin(1) of the ADC chip. MAKE SURE the p-to-p voltage is

around 2 V, or you can burn the chip.

You can generate any wave form, but you need to see some oscillation on the oscilloscope.

Digital To Analog Chipset (1) We will use the AD1886 DAC, a

amplifier and two discrete packs. Since I can’t copy the connection

picture, you can just look it up online.

Only three wires to the xilinx chip, LL, DL and CLK

Digital To Analog Chipset (2) DL, sometimes called LD, is Data Left.

Serial input to the DAC We only use half of the DAC, so we ignore

DR. LL.L, the falling edge of the LL causes

the last 16 bits clocked into the serial register shifted into the DAC

Clock is just a 8 MHz clock. DAC takes two’s compliment.

Oscilloscope Connect the ground together, and

connect the clip to the output of the Amplifier.

Then hit AUTO SCALE. You should see the wave form

generated by the function generator.

Control Logic (1) A TO D

Control Logic (2) D TO A

What to remember Do wire wrapping before lab, it takes a

while. (it’s hard to make it neat, cuz the distance between the pin is very short.)

Understand what each chip does, and the control signals

Understand why was the control signal setup that way, and why it works, or why it doesn’t work.

Some Final notes This lab is easy, this means:

Don’t worry about it! It’s not gonna be nearly as hard as the

previous check points. You should spend more time to prepare the

midterm than this lab. (Most of you will do that anyways.)

It gives you a chance to catch up on the previous labs.

GOOD LUCK ON THE MIDTERM!!!