I'm testing the possibility of AD9789 to work with multi-channel output.
To test it I built a DDS with FPGA and send to DAC the data in 16-bit wide
Complex Mode on 32-bit bus. I have connected all bus, clock and power.
After powerd on I have follow Page 62 to init DAC without any problem.
The DAC is so configured:
Fdac = 2048 MHz
Foutput RF central = 474 MHz
Interpolatro factor is 16 (2^4, Filter 0 = bypass)
DCO output fequency = 64 MHz (Fdacclk / 32)
FS buad rate is 9.14285 MHz (P/Q = 7/8)
Configuration meets the constraints :
Fdac = I * P/Q * 16 * Fbaud
I activated a "Channelizer Mode" and only Channel 0 is on.
This is all Register :
0x06, 0xC1 // Set up digital datapath
0x07, 0x00 //
0x08, 0x0D //
0x09, 0x20 //
0x0A, 0xFF //
0x0B, 0xFF //
0x0C, 0xB3 //
0x0D, 0x00 //
0x0E, 0x00 //
0x0F, 0x00 //
0x10, 0x00 //
0x11, 0x00 //
0x12, 0x00 //
0x13, 0x00 //
0x14, 0x00 //
0x15, 0x00 //
0x16, 0x00 // Set up rate converter
0x17, 0x00 //
0x18, 0x80 //
0x19, 0x00 //
0x1A, 0x00 //
0x1B, 0x70 //
0x1C, 0x3F // Set up BPF center frequency
0x1D, 0x3B //
0x20, 0xC4 // Set up interface
0x21, 0x78 //
0x22, 0x2F //
0x23, 0x00 //
0x25, 0x80 // Set up channel gain
0x26, 0x00 //
0x27, 0x00 //
0x28, 0x00 //
0x29, 0x00 // Set up spectral invert
0x3C, 0x00 // Set up full-scale current
0x3D, 0x02 //
0x05, 0x01 // Set up Channel 0 (Only)
I have setup parameter with use of register 0x1E and 0x24.
The register LTNC[2:0] is 0x00 (on register 0x21)
The register DSCPHZ[3:0] is 0x00 (on register 0x23)
The register SNCPHZ[3:0] is 0x00 (on register 0x23)
Offset out is made with FPGA to setup-holt timing.
I checked the setup-hold time with an oscilloscope and all seems ok.
Now the problems begin. I have place out signal from DDS with this
output aspect on bus :
But no output on DAC RF why ?!?!?!?
After some test I have inserted a variable latency of the I / Q data
to delay the data of x DCO cycle. after inserting some delays I got
this configuration that works. On output of DAC I have RF signal.
Why it is necessary to introduce this latency with my configuration ?
I tried to activate the other channels (CH1, CH2 and CH3) singly and are arranged as in previous figure.
How is this possible ?
Where is that wrong ?
Thanks very much.