Update 18.6.21: Sadly little progress throughout March-June (waiting for Si5351's). Anyone wishing to build a V2 kit who already has a 10-pin Si5351A-B-GT is welcome to do so - just contact me on the usual email (timbly123 at ntlworld dot com). Software is done.
Update 14.5.21: Still no sign of the Si5351 parts arriving. For now I am just going to carry on boxing up my Mk 2 as a portable receiver. Current plans are to squeeze it into a Hammond RP1175C, a plastic 185x85x55mm case with a transparent lid. If this is successful it will avoid having to make a clear window for the LCD display. I also propose mounting the Discovery board closer to the panel so that the LCD display does not have to be lifted and refitted. This will require very low-profile tactile pushbuttons if they are to fit between the Discovery and the front panel. Yes, I am now experiencing delays getting hold of push buttons!!!
Update 9.4.21: I finally get round to attaching the HA8LFK bandpass filter board. 4 x M2 pillars are used (5mm pillar with washers totalling 7mm) to secure the filter board and 8 wires to the 'presel' connector. Select filter type E in the menu and away it goes :o) The overall receiver module is very compact, although the edge-mount SMA connectors are going to have to be removed to fit it into a small 'portable receiver' sized box. Work on the CAT control interface has now resumed.
Update 5.4.21: First V2 kit has shipped! The first batch is ready to go but I only have 2 Si5351s; I am still waiting for the order I placed in early Feb to arrive.
Update 27.3.21: Just waiting for the Si5351's now, after which kits will finally be ready to go. (That said, the lead time on these chips is still pushing out to April/May. Hopefully I'm in a queue for stock and will get them before then.) The conversion of the User Interface to 8bits per pixel has finally been done and it is now so fast that display double-buffering is not required. The code no longer needs to use the SDRAM.
Update 16.3.21: It looks like Si5351A ICs have become globally scarce with massive lead times being quoted (40 weeks by some distributors). If you already have some of these (10pin TSSOP) and are interested in a kit without the Si5351 please email me, as these can probably be shipped in a week or so, otherwise we'll have to wait a few more weeks.
Update 10.3.21: Still waiting for the last few parts to arrive for kits (there are many parts experiencing long lead times at the moment). The kit price is looking to be ~ 2x that of the previous kit, however, the kit will include virtually all of the parts needed to assemble the radio PCB. (Some consultation with previous builders suggested that the supply of a full kit is preferable, particularly when you consider the postage overhead to each builder of placing multiple component orders.)
Update 25.2.21: Still waiting for various parts to arrive for kits.
Update 14.2.21: I have been working on the Mk2 receiver software: Si5351 tuning is now really clean with all PLL resets positioned 'between useful bands'. Some work still ongoing looking at UI drawing to avoid VSYNC issues. HA8LFK filter board is on order to do integration testing. The first run of PCBs has no functional mistakes so I am now looking at getting kit parts together. If you are interested, drop me an email at moc.dlrowltn@321ylbmit so I can assess numbers.
Update 10.2.21: The Mk2 receiver board is working well, including the new switched attenuator. With its slightly increased analogue gain, the Noise Figure & overload points are now: NF=16.6dB/OL@-36dBm at 0dB atten, through to NF=46.6dB/OL@-6dBm at 30dB atten. The 16.6dB NF is significantly lower than my band noise on all bands including 10m, so I will leave the gain as it is. Freq coverage is from 1.8MHz to 54MHz. As with the Mk1.2 receiver, LO quadrature, IQ balance and common-mode mixer breakthrough all get steadily worse as the FST3253 is run faster and faster - but this will be the case with all such SDR designs. Looking further into the I2C address fiasco, it turns out that pre-programmed Si5351s often end up in the supply chain, however, they will have an extended part number. This can be looked up at https://www.silabs.com/products/timing/lookup-customize parts and a datasheet addendum is sometimes available. So the take-home from this is just be aware when buying Si5351s!
Update 6.2.21: Mk2 receiver board is finally up and running with basic functionality established. The Si5351 is now working after 2 days of head scratching and pain. It turns out that Mouser have shipped me parts that do NOT have an I2C address of 0x60 as per the datasheet (apparently this is not the first time and has affected amateur NT7S as well). My chips are at address 0x62. Looking back, this took me so long to solve because, in spite of all my years' experience I simply did not entertain the idea that the address might be wrong.
Update 4.2.21: Mk2 receiver board has been powered up and the ADC subsystem is working. No bus response at all from the Si5351, and yet my code talks to an Adafruit board just fine. I suspect the chip is dead but have no explanation as to why. Trying a new chip today.
Update 1.2.21: The Mk2 receiver boards are back from the fab (JLCPCB) and thus far I have soldered all of the passives on. The chips are going on next then there is the board bring-up. None of this has been breadboarded, so this is when I discover all the mistakes in the schematic and the PCB layout!
Update 9.1.21: Work on Mk2 receiver has started. The Mk2 is going to be a plug-on 'shield' for the STM32F429I Discovery board. It has a cheaper BOM through the use of lower cost parts, including a Silabs Si5351 for the synthesiser in place of the more expensive AD9952 DDS (which was smoother and effectively went down to DC). A digitally controlled attenuator has been added and will provide dynamic range extension without affecting the S meter reading.