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Hi all. Just a word of warning/advice.
The Si5351 based VFO (clock) boards produced by Hans (QRP Labs) and Adafruit are not directly interchangeable for use within the many Arduino based VFO sketches that are appearing out there.
The reason for this is that the boards use different crystal frequencies for their operation.
The QRP Labs board is based on a 27MHz crystal while the Adafruit board is based on a 25MHz crystal.
Although both boards have the same basic 7 active connections (Gnd, Vcc, SCL, SDA, OP1, OP2, OP3) and while they CAN theoretically be used virtually interchangeably, you will need to compensate for which board you are using within the coding within the relevant .ino sketch file when using an Arduino based version.
The QRP Labs VFO is designed around Han's version of the Si5351 board and the VFO will not produce the correct output frequencies if an Adafruit board is kludged into it instead.
It can be done but at the low price and high quality of Han's kit it really isn't worth the effort - and I prefer Han's boards anyway :-)
Slim G4IPZ
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Am I missing something or can't the software be changed to account for the difference? Our VFO has a timing constant in the code that is changed to account for variations in the 125MHz crystal on the AD9850 board. Indeed, one of our users uploaded an Excel app that calculates the constant for you. (Thanks, Norbert.) My guess is that something could be done in software to account for the differences.
Jack, W8TEE
From: "special@... [BITX20]"
To: BITX20@...
Sent: Tuesday, December 6, 2016 10:15 AM
Subject: [BITX20] Si5351a VFO boards.
?
Hi all. Just a word of warning/advice.
The Si5351 based VFO (clock) boards produced by Hans (QRP Labs) and Adafruit are not directly interchangeable for use within the many Arduino based VFO sketches that are appearing out there.
The reason for this is that the boards use different crystal frequencies for their operation.
The QRP Labs board is based on a 27MHz crystal while the Adafruit board is based on a 25MHz crystal.
Although both boards have the same basic 7 active connections (Gnd, Vcc, SCL, SDA, OP1, OP2, OP3) and while they CAN theoretically be used virtually interchangeably, you will need to compensate for which board you are using within the coding within the relevant .ino sketch file when using an Arduino based version.
The QRP Labs VFO is designed around Han's version of the Si5351 board and the VFO will not produce the correct output frequencies if an Adafruit board is kludged into it instead.
It can be done but at the low price and high quality of Han's kit it really isn't worth the effort - and I prefer Han's boards anyway :-)
Slim G4IPZ
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You're not missing anything, Jack. It is falling-off-a-log easy to change the code from 25 or 27MHz. It's not an issue, other than being aware of it. NT7S's documentation makes it very clear.
73,
Todd K7TFC
On Dec 6, 2016 7:43 AM, "Jack Purdum econjack@... [BITX20]" < BITX20@...> wrote:
?
Am I missing something or can't the software be changed to account for the difference? Our VFO has a timing constant in the code that is changed to account for variations in the 125MHz crystal on the AD9850 board. Indeed, one of our users uploaded an Excel app that calculates the constant for you. (Thanks, Norbert.) My guess is that something could be done in software to account for the differences.
Jack, W8TEE
?
Hi all. Just a word of warning/advice.
The Si5351 based VFO (clock) boards produced by Hans (QRP Labs) and Adafruit are not directly interchangeable for use within the many Arduino based VFO sketches that are appearing out there.
The reason for this is that the boards use different crystal frequencies for their operation.
The QRP Labs board is based on a 27MHz crystal while the Adafruit board is based on a 25MHz crystal.
Although both boards have the same basic 7 active connections (Gnd, Vcc, SCL, SDA, OP1, OP2, OP3) and while they CAN theoretically be used virtually interchangeably, you will need to compensate for which board you are using within the coding within the relevant .ino sketch file when using an Arduino based version.
The QRP Labs VFO is designed around Han's version of the Si5351 board and the VFO will not produce the correct output frequencies if an Adafruit board is kludged into it instead.
It can be done but at the low price and high quality of Han's kit it really isn't worth the effort - and I prefer Han's boards anyway :-)
Slim G4IPZ
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Good to know. My mission is to see more ham projects using microcontrollers and this seems like a good fit.
Thanks!
72,73, Jack, W8TEE
From: "'Todd F. Carney / K7TFC' k7tfc@... [BITX20]"
To: BITX20@...
Sent: Tuesday, December 6, 2016 12:35 PM
Subject: Re: [BITX20] Si5351a VFO boards.
?
You're not missing anything, Jack. It is falling-off-a-log easy to change the code from 25 or 27MHz. It's not an issue, other than being aware of it. NT7S's documentation makes it very clear.
73,
Todd K7TFC
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look at that :
here you will find many interesting stuff. 9a3xz,Mikele?
?
Good to know. My mission is to see more ham projects using microcontrollers and this seems like a good fit.
Thanks!
72,73, Jack, W8TEE
From: "'Todd F. Carney / K7TFC' k7tfc@... [BITX20]" <BITX20@...>
To: BITX20@...
Sent: Tuesday, December 6, 2016 12:35 PM
Subject: Re: [BITX20] Si5351a VFO boards.
?
You're not missing anything, Jack. It is falling-off-a-log easy to change the code from 25 or 27MHz. It's not an issue, other than being aware of it. NT7S's documentation makes it very clear.
73,
Todd K7TFC
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Self explanatory -
? //initialize the Si5351
? si5351.init(SI5351_CRYSTAL_LOAD_8PF, 0); //If you're using a 27Mhz crystal, put in 27000000 instead of 0
? // 0 is the default crystal frequency of 25Mhz.
Rob G4NQX
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Be careful using N6QW, Pete Juliano's code from the LBS. The libraries for the SI5351 is incorrect. Don't get me wrong, Pete does fantastic work. Our club did the LBS as a group build and we quickly found problems with the code.
73
Ken VA3ABN
On Tue, Dec 6, 2016 at 2:28 PM, Mikele Martincic socijalizam1@... [BITX20] <BITX20@...> wrote:
?
look at that :
here you will find many interesting stuff. 9a3xz,Mikele?
|
?
Todd, I would only say that it is 'falling off a log' easy?if you can
and are willing to program your own code changes
?
The?point?of my post was simply to?inform those
amongst?the group?who are?not au fait with carrying out even
basic Arduino or Atmel AVR coding that the respective boards?are not just a
case of plug and play.
?
As I said ".....you will need to compensate for which board you are using
within the coding within the relevant .ino sketch file when using an Arduino
based version."
?
Of course if you are aiming to use a QRP Labs AVR based VFO board with an
Adafruit Si5350 break out then you will need to be able to deconstruct Han's
machine code which is not written in Arduino?C?.
?
73
?
Slim G4IPZ
?
?
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Pete, N6QW, is an absolute genius when it comes to building something, as his LBS rig proves. He's forgotten more about electronics than I will ever know.
In Tom VFO video, he uses a push button to change the VFO's frequency increment. In the original Forty-9er QST article, that's the way I wrote the code, too. However, I wrote a subsequent article in QRP Quarterly that automatically changes the increment base upon (your own) custom spin rate of the encoder. For me, I have the default set to 100Hz, so I can make very small changes in frequency. However, if I start spining the encode fast (and you define what "fast" is), it automatically changes the increment to 10KHz (or whatever you want it to be). As I approach my goal frequency, the spin rate drops and the code senses that and drops the default back to 100Hz. I find it very convenient.
Fun stuff!
Jack, W8TEE
From: "Mikele Martincic socijalizam1@... [BITX20]"
To: "BITX20@..."
Sent: Tuesday, December 6, 2016 2:28 PM
Subject: Re: [BITX20] Si5351a VFO boards.
?
look at that :
here you will find many interesting stuff. 9a3xz,Mikele?
|
There is also a hardware solution, you can easily change they 27.000 MHz crystal during the build of Hans’s Si5351a board, or install a 25 MHz TCXO as there are pads on the board for that. The TCXOs at 25MHz are not expensive. Digi-Key has them for $1.65 - Duffey KK6MC
--
KK6MC
James Duffey
Cedar Crest NM
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If you are using an Arduino to drive your vfo you should be able to write a 2 Mhz calibration offset in the code to accomodate either a 25mhz or 27mhz. Crystal. ?Typically the offset is a few khz as very few crystals are exactly on the marked frequency. ?This is because crystals are classified not only by load capacitance, but also 5ppm, 10ppm, or some op to 50ppm.
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It is not just a 2 Mhz offset that you have to change.? The oscillator is used to set the internal pll s in the 5351, and different divider ratios have to set depending on the oscillator frequency.? All si5351 libraries and code I have seen have a place to set the oscillator frequency to either 27 or 25 Mhz.?? In the NT7S library there is also a calibration adjustment that can be applied to make small adjustments to account for any slight difference in? crystal frequency
DuWayne KV4QB
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Hi all
I want to clarify a few things because there appears to be some confusion here. I have been working with the Si5351A for a long time.?
The QRP Labs VFO kit ?has a menu configuration where you enter the reference frequency. Just like the Ultimate3 QRSS/WSPR TX kit . If you wanted to use a 25MHz reference, you simply enter 25MHz in this configuration parameter instead of the default 27MHz. That's it. So it would be perfectly possible to use the Adafruit Si5351A board with the QRP Labs kits if you want. But I don't see that there would be any point. The QRP Labs Synth board ?is cheaper than Adafruit's and plugs into the sockets on the VFO PCB. The QRP Labs Synth board is already included in the $33 price of the VFO and Ultimate3S kits.?
By the way the original choice of 27MHz crystals instead of 25MHz is that I have an algorithm in the Ultimate3S which optimises for perfect 1.46Hz tone spacing for WSPR, whilst at the same time keeping to the even integer mutlisynth divisor recommendation of the datasheets, for getting best performance (lowest jitter). With a 27MHz reference, this algorithm can achieve 1.46Hz tone spacing on every amateur band from 2200m to 2m inclusive. But with a 25MHz reference, 1.46Hz tone spacing is not possible on 2m band. So therefore I chose 27MHz!
QRP Labs has lots of sample code:
AVR C code using both the I2C peripheral and bit-banged? Adapted to Arduino sketch by Alf VK2YAC? Adapted to Arduino sketch by Christophe OE1CGS? Adapted to PIC sketch by Russ G4SAQ?
All of the QRP Labs products firmware and all of this sample code, can use either 27MHz reference or 25MHz reference and will correctly adapt accordingly. In the sample code you just change the constant from 27000000 to 25000000. Simple as that.?
A lot of Si5351A libraries, including NT7S, are based on a Si5351A Linux driver. That driver may be fine on 32-bit systems but it was too inefficient and too large for 8-bit systems. It is also harder to understand the code. When I originally wrote my Si5351A code it had to fit in the 32KByte program space of the ATmega328 used in the Ultimate3S kit. The code also has to manage the user interface (LCD/buttons), the GPS discipline, and all the functions and features, as well as all the encoding for the supported modes CW, WSPR, Hell, JT9, JT65, PI4, Opera, ISCAT etc. Therefore my Si5351A code had to be compact! So you will find that the samples (links above) are as simple and straightforward as possible, for this reason.?
Finally - QRP Labs have an Arduino shield kit??($14) which has sockets for the QRP Labs Si5351A Synth board, or AD9850 DDS module; it also has sockets for the QRP Labs LPF module. This Arduino shield could be used with the Si5351A Synth for people wanting to write their own VFO code.? ? 73 Hans G0UPL
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Todd K7TFC
Tom Clifton
DuWayne Schmidlkofer