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PicoZed SDR 7035/AD9361 SOM / Sync'ing multiple AD9361 devices

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DSP_1
Moderator(1)
PicoZed SDR 7035/AD9361 SOM / Sync'ing multiple AD9361 devices

Many applications call for synchronized multiple RF inputs/outputs (MIMO), including phase array processing, beamforming, adaptive antennas, etc.

As described in http://wiki.analog.com/resources/eval/user-guides/ad-fmcomms5-ebz/multi-..., there are (2) aspects to synchronizing multiple AD9361’s across PicoZed SDR SOMs.

• Sample clock Synchronization

o Each AD9361 includes its own baseband PLL that generates sampling and data clocks from the reference clock input. A logical SYNC_IN pulse input is needed to align each device’s data clock with a common reference. On PicoZed 7035/AD9361 SOM, the AD9361 'SYNC_IN' (pin H5) is connected to / driven from Z7035 IO_L10_35_SYNC_IN (pin G15).

• RF (LO) Synchronization
o The AD9361 does not include RF synchronization internally. Techniques to resolve phase difference of the RF PLLs across different AD9361 are discussed in http://wiki.analog.com/resources/eval/user-guides/ad-fmcomms5-ebz/multi-....

At this time the PicoZed SDR FMC carrier card is not intended to have more than one SOM. Therefore there is no (simple) connection to drive a common SYNC_IN to multiple SOMs / AD9361. Future PicoZed SDR carriers may provide such functionality.

It might be possible to drive a replica of ‘SYNC_IN’ from the Zynq down through a custom PMOD output on a ‘master’ carrier, then over a custom cable to a PMOD input of a ‘slave’ carrier, and finally from Zynq to the ‘slave’ AD9361 SYNC_IN. Skew would need to be somehow matched across the master / slave SYNC_IN signals. However, this isn’t a use case that we have specifically planned for. The user would need to do some experimentation.

rpc0618
Junior(0)
To Generate SYNC_IN pulse...

Forgive my ignorance in this field, and take note that I don't have any experience with clocking multiple devices yet.

With that being said, I was just starting to look into this kind of thing today (syncing event timing across multiple devices). I'm wondering if you couldn't just use IEEE 1588 (Precision Time Protocol) in order to generate a SYNC_IN pulse across multiple devices.

reference: http://www.wiki.xilinx.com/Zynq-7000+AP+SoC+-+Precision+Timing+with+IEEE...

Perhaps this is meant for use across "devices" of a higher computational order with greater (spatial?) separation, or maybe only using an ethernet-type link... but if they've already solved this problem before, I figure the logic of how to do it might be very similar.

Just some thoughts in the off chance that it helps.

DSP_1
Moderator(1)
Re: PicoZed SDR 7035/AD9361 SOM / Sync'ing multiple AD9361's

Just to clarify, customers intent on synchronizing AD9361’s across multiple SOMs could design their own custom carrier board connecting the AD9361 'SYNC_IN' signals through the respective Zynq devices. PicoZed SDR SOM (AES-Z7PZ-SDR2-G) was indeed designed to support this through the AD9361 'SYNC_IN' (pin H5) connected to / driven from Z7035 IO_L10_35_SYNC_IN (pin G15).

mbrown
Moderator(7)
Additional clock info

Additional info that may help (from this thread -- http://picozed.org/content/picozed-sdr-info)
PicoZed SDR provides an on-board 40MHz crystal and an external clocking option for the AD9361 by using an analog multiplexor (ADG772).  If an external oscillator is used, the frequency can vary between 10 MHz and 80 MHz.  The selection between the two clock sources is under control of a Zynq PL pin in Bank 34 (K11).

The external clock signal is provided by a custom carrier board through the micro headers on the bottom of the SOM.  As such, the same clock can be routed to the Zynq device if syncrhonization between BBP and RF devices is required.

Jaco Naude
Junior(0)
Details on AD9361 pins available to custom baseboard

One of my customers is considering developing their own custom baseboard in order to sync multiple PicoZed-SDRs. Would it be possible to provide details on which AD9361 pins are exposed through the connectors at the bottom of the SOM (even if they have to be routed through PL)?

Many thanks,
Jaco

mbrown
Moderator(7)
List of AD9361 signals at the SOM connector

Here you go Jaco.  Feel free to contact me via email if you need further clarification.
 
List of AD9361 signals at the SOM connector:
 
AD9361_GPO0
AD9361_GPO1
AD9361_GPO2
AD9361_GPO3
AD9361_AUXADC
AD9361_AUXDAC1
AD9361_AUXDAC2
AD9361_GPO_PWR
AD9361_CLK
 
As stated earlier in this thread:
On PicoZed 7035/AD9361 SOM, the AD9361 'SYNC_IN' (pin H5) is connected to / driven from Z7035 IO_L10_35_SYNC_IN (pin G15).
 
-Matt
 

Jaco Naude
Junior(0)
Thanks Matt.

Thanks Matt.