BladeRF A4 - Clock Select Issue

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slaw1982
Posts: 1
Joined: Wed Mar 06, 2019 6:58 am

BladeRF A4 - Clock Select Issue

Post by slaw1982 »

I am trying to setup two BladeRF A4 boards that share a clock. The first BladeRF uses a 10MHz input to REFIN and then is configured to output the 38.4MHz clock via CLKOUT. Everything seems to work fine with this setup.

The second board i try to setup to accept the clock from the first board via the CLKIN pin using the:
set clock_sel external

The system pauses for a few seconds before returning an error:

[ERROR @ host/libraries/libbladeRF/src/backend/usb/nios_access.c:78]
Failed to receive NIOS II response: An unexpected error occured
[ERROR @ host/libraries/libbladeRF/src/board/bladerf2/bladerf2.c:3487]
bladerf_set_clock_select: dev->backend->config_gpio_write(dev, gpio) failed:
An unexpected error

Any ideas why this is failing?

Thanks
robert.ghilduta
Posts: 156
Joined: Thu Feb 28, 2013 11:14 pm

Re: BladeRF A4 - Clock Select Issue

Post by robert.ghilduta »

It appears that the second slave bladeRF micro may not be receiving a clock.
Can you please run bladeRF-cli with --verbosity=verbose? Are you sure CLKOUT is enabled on the master? What kind of cable are you using? Perhaps trying a shorter, less lossy UFL might help as well.
HB9FXX
Posts: 3
Joined: Fri Jun 18, 2021 4:17 am

Re: BladeRF A4 - Clock Select Issue

Post by HB9FXX »

Got exactly the same behavior.

Using

Code: Select all

set clock_ref true
to lock to an external 10MHz ref clock on the ref clock connector works fine, using

Code: Select all

set clock_sel external
to use a 38.4MHz clock on the clock in connector results in the same timeout error.

Using a Leo Bodnar GPSDO (3.3V CMOS output) without attenuator, tried with several drive currents. The ref clock input even locks if a 10dB attenuator is used (ref clock is also specified to support lower clock levels).

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Last edited by HB9FXX on Sun Jul 04, 2021 2:53 am, edited 1 time in total.
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