I'm proceeding with the zBITX project using the FDIM "hat" and compendium article. Farhan suggested that users might learn a bit about DSP programming. I hope I might get to some of that, plus learn to use KiCAD and also learn some procedures for building complex C files in Linux and specifically learn a bit about the use of github for projects. This might be a long post so I'll try to break it into sections.
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Crystal Filter
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This was my first KiCAD project and I'm pleased with it despite a non-fatal error or two. Soldering in those tiny crystals was scary, but successful. Here's a section of the board with the crystals shown at the top, and a 1206 resistor for comparison:
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My crystals required ~4.5 pF capacitors rather than the 2.2 pF in the schematic. Two part numbers were mentioned and I may have selected the wrong one.? (I used ABM8-40.000MHZ-B2-T from Mouser. The other option was ABM10AIG-40.000MHz-2Z-T.) My response curve isn't great but I think it'll do for now.? It's about 22 kHz wide and the high side roll-off isn't pretty.
The vertical scale is 10 dB/division and horizontal is 5 kHz/division.
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OLED display
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I'm not sure if I'm using the right type or not. It's a 0.96", 128x64.? I wasn't sure which I2C interface to connect to, so I tried them all with no output seen. Is it supposed to be the _BB "bit-banging" version?
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One person reported a missing file message regarding the OLED. I haven't experienced that but am still interested in Farhan's response of August 6, 2024 about the branch. Which leads to ...
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Github, branches, 64 versus 32 bit ??
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I started with a memory card image from Farhan. It ran on my Pi 4B and showed the program on my HDMI monitor.? Following later discussions, I upgraded (I guess) to the 64 bit image posted by JJ.? It also ran OK, showed output, controlled the Si5351a in the hat.
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Now, are there 32 bit and 64 bit realms out there?? If I follow Farhan's instructions on the OLED file, will it work with my current 64 bit system?? How does a branch work?? Is it a complete set of source code for the entire project, with some changes to its parent version?? I obviously need to go to school on github. Is the Farhan branch the right thing for me to be using with the zBITX project?
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OK, that's enough for now.? I've completed a KiCAD board for the superhet section, but am trying to be patient and make sure I have it the way I want it before ordering the board.
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73
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Nick, WA5BDU
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Nick Kennedy