[minima] Re: Auto-calibration of the Si570 + some refactoring
- From: Frank Ross <w4nhj@xxxxxxxxxxx>
- To: "minima@xxxxxxxxxxxxx" <minima@xxxxxxxxxxxxx>
- Date: Tue, 11 Feb 2014 06:46:42 -0500
Hi all,
Take a look at the way you can calibrate the Elecraft K3. You can download the
manual free from their site. You don't need a counter and you can calibrate to
within 1 or 2 Hz using WWV.
It works, I've done it.
Frank - W4NHJ
Sent from my iPad
> On Feb 11, 2014, at 4:24 AM, Thomas Sarlandie <thomas@xxxxxxxxxxxxx> wrote:
>
> That is a very interesting idea but I think the frequency error would be much
> larger than what we get with pre-calibrated output.
>
> Take this page for example:
> http://jorisvr.nl/arduino_frequency.html
>
> Mentions an error of +105 ppm over 24 hours with a 16mhz quartz. I am
> assuming it was in a room where the temperature did not change much. The
> maximum error with factory calibration is specd to be lower than 61.5ppm over
> the full range of temperature of the chip.
>
> How do the pic based frequency counter works? They must have some pre-scaler
> and a pretty stable clock?
>
> thomas
>
>
>
>> On Tue, Feb 11, 2014 at 1:13 AM, Dave <dave@xxxxxxxxxx> wrote:
>> Steve:
>> It should be possible to write a small routine(microprocessor pin would be
>> needed) to do the frequency counting function. Accuracy would depend on the
>> accuracy of the 16 MHz crystal. That could make the calibration automatic
>> only requiring a button push to initiate. The program could program a
>> frequency that is low enough for the micro to count it(say 10 MHz), compare
>> the measured to commanded and then calculate the Si570 crystal frequency.
>>
>> Dave - WB6DHW
>> <http://wb6dhw.com>
>>
>>
>>> On 2/11/2014 12:07 AM, Steve VK2SJA wrote:
>>> Some random thoughts:-
>>>
>>> Two calibration methods exist.
>>>
>>> 1. Manually enter the start-up frequency. Software uses this value along
>>> with additional values retrieved from the Si570 chip to calculate the
>>> actual reference crystal value.
>>>
>>> 2. Instruct Si570 to output known frequency, say 10Mhz and adjust up and
>>> down the software crystal reference value until the output on a frequency
>>> counter is exactly 10Mhz.
>>>
>>> Both methods have some Pros and Cons.
>>>
>>> Method 1:-
>>> You don't need a Frequency Counter
>>> You need to know your Si570 start-up frequency (might prove awkward
>>> finding this out without a counter - negates not needing one)
>>> Accuracy is good. But Tomas's own results seem to show that +/- 300 Hz
>>> might not be an unreasonable expectation.
>>>
>>> Method 2:-
>>> You DO require a frequency counter of some sort.
>>> Accuracy will only be as good as the counter.
>>> You don't need to know the Si570 start-up frequency.
>>> It is probably reasonable to expect errors of only +/- 3 Hz after
>>> calibration
>>>
>>> Not every person owns a Frequency Counter. I will even allow that it is
>>> possible that someone building a Minima may not own one.
>>>
>>> So I would actually suggest having both methods available via a Firmware
>>> set-up routine. Since most of the extra code would deal with changing a
>>> value via the VFO pot. And both methods require this. A significant
>>> portion of the code should be able to be shared between both methods.
>>>
>>> I'm thinking something along the lines of:-
>>>
>>> Press and hold Function button while powering up Minima to enter setup
>>> routine. Use VFO knob to cycle through setup options. Press enter to
>>> select the one you want. One option can be to exit setup. Something like
>>> this:-
>>>
>>> Setup
>>> Calibrate 1 -> Calibrate 2 -> Other Options we haven't thought of yet ->
>>> Quit -> Back to Calibrate 1
>>>
>>> When you enter either Calibrate 1 or 2 the user interaction is much the
>>> same. With one you are adjusting the crystal reference frequency up and
>>> down until you get exactly 10Mhz on the counter. With the other you are
>>> adjusting the value of the start-up frequency up or down until it matches
>>> your known Si570 start-up frequency. In both cases you press the Function
>>> button to accept and save the new value. Which returns to the top level
>>> setup menu.
>>>
>>> There is even a logical progression in doing both calibration routines in
>>> order 1 and 2. While entirely non-essential Calibrate 2 could use the
>>> calculated value produced by Calibrate 1 as its starting point. Which
>>> would put it very close to the correct value.
>>>
>>>
>>> Anyway just some random thoughts out loud.
>>>
>>> 73, Steve.
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>> Thomas,
>>>>
>>>> Just to be clear, what I am suggesting is that the calibration
>>>> procedure would initially present on the display a 'common'
>>>> start-up frequency for the Si570. As an example, the CMOS
>>>> Si570 that is sold by KM5H
>>>> http://km5h.softrockradio.org/index.php?route=product/product&product_id=49
>>>> has a start-up frequency of 56.32 MHz. If it is agreed upon that
>>>> that start-up frequency is commonly used, then that would be the
>>>> frequency value initially presented to the operator. If the
>>>> Si570 actually being used has a different start-up frequency,
>>>> then the operator can use the potentiometer to change the initial,
>>>> value to the actual value. For example, the CMOS Si570 that I
>>>> have has an initial start-up frequency of 10 MHz, so I would
>>>> adjust the frequency setting displayed accordingly prior to
>>>> pushing the function button to accept the value displayed. I
>>>> hope this makes sense to you.
>>>>
>>>> 73,
>>>>
>>>> Mac AE5PH
>>>>
>>>>> On 02/10/2014 12:24 PM, Thomas Sarlandie wrote:
>>>>> Dan,
>>>>>
>>>>> Latest version of my code will always be available in my github
>>>>> repository:
>>>>> https://github.com/sarfata/radiono
>>>>>
>>>>> The code I was mentioning yesterday has already been merged by Farhan
>>>>> and so you will get all my changes in the official version which is
>>>>> available here:
>>>>> https://github.com/afarhan/radiono
>>>>>
>>>>> The rest of the discussion is about what is the best way to calibrate:
>>>>> 1 - Using factory calibration settings in the chip - but we need a
>>>>> way for the user to find out this frequency and give it to the program
>>>>> (maybe through a menu like what Mac suggested)
>>>>> 2 - Starting with no calibration and a fixed output frequency
>>>>> (10Mhz). Ask the user to adjust until it is perfectly 10mhz.
>>>>>
>>>>> Both method will play nicely with my changes. Nothing was lost ;)
>>>>>
>>>>> best,
>>>>> thomas
>>>>>
>>>>>
>>>>> On Mon, Feb 10, 2014 at 9:50 AM, Dan Reynolds <on30ng@xxxxxxxxx
>>>>> <mailto:on30ng@xxxxxxxxx>>wrote:
>>>>>
>>>>> Thomas, I would still like to see your code if possible.
>>>>>
>>>>>
>>>>> 73
>>>>> Dan -- KB9JLO
>>>>> https://sites.google.com/site/on30ng/
>>>>>
>>>>>
>>>>> On Sun, Feb 9, 2014 at 8:27 PM, Thomas Sarlandie
>>>>> <thomas@xxxxxxxxxxxxx <mailto:thomas@xxxxxxxxxxxxx>>wrote:
>>>>>
>>>>> Hi everyone!
>>>>>
>>>>> Spent some time this week-end on the Radiono software. I found
>>>>> out earlier this week that my Si570 had a very large error
>>>>> that grew linearly with frequency. We quickly found out that
>>>>> each module is different and you need to use calibration
>>>>> information that is saved in the module. The current source
>>>>> code has Farhan's si570 calibration hardcoded in. That will
>>>>> most likely not work for you.
>>>>>
>>>>> I have updated the Radiono source code to automatically get
>>>>> the calibration information and calculate the crystal
>>>>> frequency every time we start the program. The only
>>>>> information that needs to be defined in the source code is the
>>>>> default frequency programmed by the factory. In my case it was
>>>>> 56.320 but your mileage may vary.
>>>>>
>>>>> There are two ways to find this frequency:
>>>>> - Spec: Look on the marking on your Si570 (mine says
>>>>> CAC000141) and lookup some tables online to find which
>>>>> frequency corresponds to your marking (I cant find this table,
>>>>> if someone has it, please share!)
>>>>> - Experimental: just remove the Arduino and apply power to
>>>>> the control board. Measure the frequency at the output of the
>>>>> Si570.
>>>>>
>>>>> I have updated the wiki:
>>>>> http://www.hfsignals.org/index.php/Si570
>>>>>
>>>>> The updated source code has been submitted to Farhan in a
>>>>> pull-request:
>>>>> https://github.com/afarhan/radiono/pull/4
>>>>>
>>>>> Full list of changes:
>>>>>
>>>>> Split the Si570 code in a separate class.
>>>>>
>>>>> In the Si570 class:
>>>>> * Use the factory-calibrated output frequency to automatically
>>>>> calculate the internal crystal frequency and use that instead
>>>>> of hard coded values.
>>>>> * During initialization detect errors talking to the Si570.
>>>>> * Use multi-bytes i2c reads and writes when possible (ie:
>>>>> read/write multiple bytes without re-starting a transaction).
>>>>> Only works for read/writes in consecutive registers.
>>>>> * Use types with explicit size where that makes sense (uint8_t
>>>>> instead of char, uint64_t, etc)
>>>>> * Added some debugging on the serial console through a "debug"
>>>>> function
>>>>>
>>>>> In the main sketch:
>>>>> * Show a message on the LCD if the Si570 is unreachable.
>>>>> * Initialize the serial port for debugging
>>>>> * Fix some compilation warnings with string litterals being
>>>>> casted to char*
>>>>> * Removed unused variables
>>>>>
>>>>>
>>>>> And now, back to the soldering iron!
>>>>>
>>>>> 73,
>>>>> thomas
>
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