Farhan,
Thanks for pulling my changes!
If I understand correctly the process in your video, you are basically
re-calibrating the Si570 and not using the values that were set at the
factory. Is this correct?
I have found the factory calibration values to be very accurate:
https://docs.google.com/spreadsheet/ccc?key=0As9CZnZ-A5a2dEZaM1dlWVdVX3pXaUlJMXd0cHNscHc#gid=2
Do you have any reason to stay away from the factory calibration?
I think the advantage of working with this factory frequency and the
factory set calibration are:
- You do not need to make precise measurement of frequencies - you
just need to find out what "type" of si570 you have (10mhz, 56.320mhz,
etc)
- It's easier for the "operator": You do not need to understand how
the si570 works internally and do the maths. It's not
super-complicated but it will waste at least a few hours of everyone.
We just need to figure out what are the possible "factory frequencies"
and we could have a menu that asks you to choose (or enter) yours the
first time you run the radiono. We can save that in the EEPROM or the
calculated xtal.
Of course, we could also leave the option for people who want to
re-calibrate their si570 manually to do so.
Very excited about the serial protocol. Almost started something today
to set the frequency from my computer when I was measuring the error
at different frequencies. We need this!
73,
On Sun, Feb 9, 2014 at 7:19 PM, Ashhar Farhan <farhanbox@xxxxxxxxx
<mailto:farhanbox@xxxxxxxxx>>wrote:
thomas, i have pulled the changes. i was just wondering if there
should be a caliberation procedure that is independent of the
si570 marking. i have used this in sweeperino. check
http://www.youtube.com/watch?v=qRNOp1F81i8a 1:10 onwards. It
caliberates a number of things, but essentially, the process is this:
1. Set the Si570 to 10 Mhz while using the hard-coded xtal value.
2. Measure the frequency. If the crystal freq. is the same as hard
coded value, the output will be exactly at 10 Mhz. Let's consider
the measured frequency to be M. If M is higher, the crystal's
actual frequency is higher, if M is lower, it is lower.
3. The actual frequency of the internal crystal = (M/10,000,000) *
XTAL_FREQ.
Here is what I suggest we can do:
1. Store the xtal frequency in the eeprom memory of the radiono,
(so that it does not forget it when powered down.
(http://arduino.cc/en/Reference/EEPROM)
2. Using the serial port, send the newly calculated xtal frequency
to radiono. radiono overwrites the original.
The serial port protocol has to be written. I am starting a
separate thread for that.
- f
On Mon, Feb 10, 2014 at 8:15 AM, Steve VK2SJA <vk2sja@xxxxxxxxxxx
<mailto:vk2sja@xxxxxxxxxxx>>wrote:
Great work Thomas. Thanks!
> 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
>
