AD9911DDS

AD9911DDS Release status: experimental [box doku]
Description	Direct Digital Synthesizer
Author(s)	siro
Last Version	0.1
Platform	*
License	GPL

*TODO upload pictures*

AD9911DDS

This project describes the AD9911 Direct Digital Synthesizer. It is capable of generating a sine-wave between 250Mhz and >1Hz. The created evaluation unit is descripted here.

The Hardware

CLK_MODE_SEL = 1.8V
Rset = 1k91
crystal 25Mhz
DVDD 1.8V
AVDD 1.8V
DVIO 3.3V
SDIO_0 MOSI
SDIO_2 MISO

channels

There are four channels:

channel 0: aux channel
channel 1: primary channel
channel 2: aux channel
channel 3: aux channel

channel 1 is connected to the DAC. all aux channels are capable of modulating channel 1.

modes of operation

single tone (frequency,amplitude,phase adjustable)
2 tone test mode (amplitude modulated single tone)
2/4/8/16 FSK/ASK/PSK
frequency/amplitude/phase ramp up
frequency/amplitude/phase ramp down
frequency/amplitude/phase sweep

SPI interface

default
2-wire SPI mode, SDIO_0 is bidirectional !

SPI write
- CPOL=0
- CPHA=0
SPI read
- CPOL=1
- CPHA=1

3-wire SPI mode

configure 3-wire SPI mode using reg 0
set msb mode (default) using reg 0
SDIO_0 is MOSI
SDIO_2 is MISO

MSB/LSB mode

MSB
- the Most Significant Bit is transfered first
- the Most Significant Byte is transfered first
LSB
- the Least Significant Bit is transfered first
- the Least Significant Byte is transfered first

register select

register 0, 1, 2 are independent
channel register 0x03 - 0x18 are written to using the enable bits in register 0
you can write to multiple channels at once !

*TODO upload files*

The Software

I've created a simple programm that runs on teensy 2.0 (ATMEGA32U4). It should run on any ATmega, just change the I/O ports.
Timings are not critical, as the ATmega is much slower than the maximum I/O updaterate of the AD9911.

*TODO upload files*

Changes applied to Hardware

pull PWR_DWN_CTL low
pull SDIO_3 low
terminate IDAC with 50 Ohms agains AVCC
terminate !IDAC with 50 Ohms agains AVCC
include a 5th order low pass filter
include a transformer
series resistance for SPI interface

Results

*TODO upload pictures*