开云体育

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.?

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