[minima] Re: Si570 error: linear with frequency
- From: "Steve VK2SJA" <vk2sja@xxxxxxxxxxx>
- To: minima@xxxxxxxxxxxxx
- Date: Fri, 7 Feb 2014 20:33:31 +1100
Thanks Dave for the correction.
Got it now.
73, Steve
> Steve:
> No, don't do that. The start up frequency is NOT the crystal
> frequency. It is like any programmed frequency except it's divide
> ratios are stored in ROM.
> Adjust the number in the
>
> #define FREQ_XTAL (114292532l)
>
> until the programmed(not startup) frequency is correct.
>
> Dave - WB6DHW
> <http://wb6dhw.com>
>
> On 2/6/2014 11:55 PM, Steve VK2SJA wrote:
>> These Si570's appear to be available with lots of different start-up or
>> clock frequencies. i admit to being a bit confused about the
>> relationships
>> startup vs clock here. But you can arrive at the start up frequency from
>> the part number. See the chip datasheet part ordering section for
>> details.
>>
>> Suggestion. Apply power to Si570 chip while disconnected from I2C. To
>> make
>> sure software does not change frequency. Measure frequency output.
>>
>> Change code line below to match your default power up frequency:-
>>
>> #define FREQ_XTAL (114292532l)
>>
>> What does it look like now?
>>
>> Yes I think we are going to need a once only setup routine in firmware.
>> Si570 chip seems to store stuff like the startup frequency in registers.
>> Unclear at this point if we store offset data in NV storage in AVR or if
>> you can update Si570 registers. Still reading... Learning...
>>
>>
>>
>>> Hi,
>>>
>>> I finalized the digital board tonight and was checking the output
>>> frequency
>>> of the si570 and I found a somewhat important error which seems to be
>>> related to the vfo frequency.
>>>
>>> [image: Inline image 1]
>>>
>>> This error seems to be linear and could easily be corrected in software
>>> but
>>> for example when I set 14.200 on the VFO, my frequency meter counts
>>> 34.2133
>>> mhz.
>>>
>>> Is this something you are seeing as well? Should we add a calibration
>>> step
>>> to measure and correct this error? Or is my Si570 just bad?
>>>
>>> Full measures here:
>>> https://docs.google.com/spreadsheet/ccc?key=0As9CZnZ-A5a2dEZaM1dlWVdVX3pXaUlJMXd0cHNscHc#gid=2
>>>
>>> cheers,
>>> thomas
>>>
>>
>>
>>
>>
>
>
>
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