Setting up the Mirny external clock

Eliana

Hi,

We have an artiq with a Mirny module.
We want to set up the Mirny to run using the external clk, with a 10MHz clock,
but I can't figure out how.

I tried to change the device_db file from:
device_db["mirny0_cpld"] = { "type": "local", "module": "artiq.coredevice.mirny", "class": "Mirny", "arguments": { "spi_device": "spi_mirny0", "refclk": 100000000.0, "clk_sel": 0 }, }

to:

device_db["mirny0_cpld"] = { "type": "local", "module": "artiq.coredevice.mirny", "class": "Mirny", "arguments": { "spi_device": "spi_mirny0", "refclk": 10000000.0, "clk_sel": 1 }, }

but that did not work.

I would appriciate help, thanks in advance! 🙂
Eliana

Eliana

Hi,

I understood that "clk_sel" has to be 2 or SMA:
device_db["mirny0_cpld"] = { "type": "local", "module": "artiq.coredevice.mirny", "class": "Mirny", "arguments": { "spi_device": "spi_mirny0", "refclk": 10000000.0, "clk_sel": "SMA" }, }

However, I still can't get a Mirny output using an external 10 MHz clock.
When I run this minimal code:

`from artiq.experiment import*

class MirnyTest(EnvExperiment):
def build(self):
self.setattr_device("core")
self.setattr_device("mirny0_ch0")
self.setattr_device("mirny0_cpld")

@kernel 
def run(self):  
    self.core.reset()                                      

    self.mirny0_cpld.init()
    delay(10 * ms)
    self.mirny0_ch0.init() 
    delay(50 * ms)
    self.mirny0_ch0.set_frequency(125*MHz) 

    delay(10 * ms) 
    self.mirny0_ch0.set_att(0*dB) 
    delay(5 * ms)
    self.mirny0_ch0.sw.on()
                         
    self.core.break_realtime()`

This works with the internal clock, but with the external clock the green light is on (and only it), but I do not see any output on the scope.
It doesnt work also when I restart the artiq by taking it out of the electricity and putting it back in.
I tried 2 different clock sources, and many different voltages in the range of 0.2 to 1.5 Vppm as written in the manual. at 1.4Vpp there isnt a red light next to the green light.
I also tried different channles.

another hint: when I run the code, it fails for a few times before finally running, printing the error:
`artiq_run mirnyOn.py
Core Device Traceback:
Traceback (most recent call first):
File "<artiq>\coredevice\adf5356.py", line 97, column 17, in ... artiq.coredevice.adf5356.ADF5356.init<artiq.coredevice.adf5356.ADF5356>(...)
raise ValueError("MUXOUT not low")
^
File "mirnyOn.py", line 16, in artiq_run_mirnyOn.MirnyTest.run(..., ...) (RA=+0x13c)
self.mirny0_ch2.init()
File "<artiq>\coredevice\adf5356.py", line 97, in ... artiq.coredevice.adf5356.ADF5356.init<artiq.coredevice.adf5356.ADF5356>(...) (RA=+0x674)
raise ValueError("MUXOUT not low")
ValueError(0): MUXOUT not low

End of Core Device Traceback

Traceback (most recent call last):
File "C:\ProgramData\anaconda3\envs\artiq\Scripts\artiq_run-script.py", line 9, in <module>
sys.exit(main())
File "C:\ProgramData\anaconda3\envs\artiq\lib\site-packages\artiq\frontend\artiq_run.py", line 224, in main
return run(with_file=True)
File "C:\ProgramData\anaconda3\envs\artiq\lib\site-packages\artiq\frontend\artiq_run.py", line 210, in run
raise exn
File "C:\ProgramData\anaconda3\envs\artiq\lib\site-packages\artiq\frontend\artiq_run.py", line 203, in run
exp_inst.run()
File "C:\ProgramData\anaconda3\envs\artiq\lib\site-packages\artiq\language\core.py", line 54, in run_on_core
return getattr(self, arg).run(run_on_core, ((self,) + k_args), k_kwargs)
File "C:\ProgramData\anaconda3\envs\artiq\lib\site-packages\artiq\coredevice\core.py", line 140, in run
self._run_compiled(kernel_library, embedding_map, symbolizer, demangler)
File "C:\ProgramData\anaconda3\envs\artiq\lib\site-packages\artiq\coredevice\core.py", line 130, in run_compiled
self.comm.serve(embedding_map, symbolizer, demangler)
File "C:\ProgramData\anaconda3\envs\artiq\lib\site-packages\artiq\coredevice\comm_kernel.py", line 716, in serve
self.serve_exception(embedding_map, symbolizer, demangler)
File "C:\ProgramData\anaconda3\envs\artiq\lib\site-packages\artiq\coredevice\comm_kernel.py", line 698, in _serve_exception
raise python_exn
ValueError: MUXOUT not low`

or "MUXOUT not high". at the fifth time or so it runs without an error.

any idea what teh issue can be?

Thanks a lot!
Eliana

occheung

The specification on ADF5356 regarding low reference input:
For f < 10 MHz, ensure slew rate > 21 V/μs
So I guess if your rise time is too long, it may come into play.

I also noticed that ADF5356 seems much more likelier to lock at higher frequencies. So an idea would be to enable the ref_doubler in ADF5356 to increase the f_pfd from 10 MHz to 20 MHz. Note the loop filter is designed for f_pfd at 100 MHz.

I have been using a 1 Vpp 10 MHz sine wave as ref in. The PLL can lock most of the time to generate square wave output, but things like not acquiring the lock (red led) or no signals even when detecting the lock still occasionally happen.

Eliana another hint: when I run the code, it fails for a few times before finally running, printing the error:

The MUXOUT high and low are only for presence detection. Not controlling MUXOUT properly was an issue in older ARTIQ version. It should be fixed in https://github.com/m-labs/artiq/pull/2423. I do not see this in release-8/release-9 anymore.

Eliana

Thank you very much for the answer!

Indeed locking works consistently with an external 20MHz instead of 10MHz.

occheung So an idea would be to enable the ref_doubler in ADF5356 to increase the f_pfd from 10 MHz to 20 MHz.
As 10MHz doesn't require us using an additional clock system - what do you mean by enabling the ref_doubler? that is not one of the options in "artiq.coredevice.mirny module", right?
Thanks!

occheung

ref_doubler is one of the argument of ADF5356.
https://m-labs.hk/artiq/manual/core_drivers_reference.html#artiq.coredevice.adf5356.ADF5356

I think you just need to add this entry into your ADF5356 instances in your device_db.py

    "ref_doubler": True

You should read up the datasheet's description of the reference doubler. In particular:

The maximum allowable reference frequency when the doubler is enabled is 80 MHz.

Eliana

Thank you very much!