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The Venturii VDAC MID-1 Revision 2.0

A 3D render in KiCad of the second revision of the Venturii VDAC MID-1 Interface board.

A 3D render in KiCad of the second revision of the Venturii VDAC MID-1 Interface board.

This evening I submitted the second revision of the Venturii VDAC MID-1 Interface board to OshPark for fabrication. I have taken a few weeks off of my day job this Christmas and really hope that these boards arrive during my vacation so that I can solder them up and test them out. They’ve got some cool new features that I think users will like, particularly the DIY crowd.

Some “New” features of this revision:
– This revision should actually work without any mods. ­čśë I have verified each footprint matches the data sheets of the products purchased and verified that against the schematic and even examples online. It turned out that my understanding of FETs was incorrect and my original schematic had the Drain connected to Ground and the load connected to the Source, but at 12V the 5V signal was nowhere near high enough to turn it on. Also compared against my working Rev 1.0 prototype that was modded. 95% confident that there should be no surprises on this one.
  • OWI (One-Wire Interface) ports now have some cool new features thanks to suggestions from Mark and Jordan.
    • Each OWI port now has it’s own select-able Pull Up/Down 10K Potentiometer.
    • A 3-position jumper selects whether the data pin will be pulled up, down, or left floating, and a 10K Potentiometer determines how hard the data pin is pulled in the selected direction.
    • A 220 Ohm resistor in series with the wiper of the pot prevents the pin from being railed.
    • ┬áBecause of the Pull Up / Down selection, two status resistors had to be used as the polarity changes depending on which way the pin is pulled. This was FAR cheaper than trying to go to a SMD bi-color LED.
    • The status resistors on each OWI port are enabled with a jumper so that they can be disabled if their load / capacitance causes any interference on the data line.
  • As before, each OWI port can be used to talk to Dallas DS series temperature sensors (IE: the DS18B20), products in the AM230x family (digital temperature & humidity sensors) or can be used as a digital input or output pin.
  • The two shift registers that collect the four Digital Input pins, the four User Interface buttons and the 8 Configuration DIP switches have had their order changed so that the Digital Input Pins and the button register can be read without having to read the DIP switch register, which will reduce CPU load when the DIP switch is not expected to change very often (typically at all.)
  • Many mechanical refinements such as trying to align SMD components wherever possible to aid in the automatic placement thereof, etc.

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