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Re: [Xylo-SDR] Lionheart Block diagram v1.4

It would also seem to me that the reset line should be brought out to the
front panel as a pushbutton.

If you want to do this, I suggest considering the following arrangement:

1) resistor of about 1K from +5V to Vcc pin of MCP120;

2) bypass capacitor of 100 nF from Vcc pin of MCP120 to ground;

3) another resistor of about 1K from MCP120 Vcc pin to pushbutton;

4) other side of pushbutton to ground.

This will allow the MCP120 to work as intended, since it draws only 10 or 20 microamps. If the front panel button is pressed, the MCP120 Vcc will drop to about +2.5V, which tells it to assert reset with its internal timeout to protect against contact bounce noise being coupled into the RESET line. It also assures it has enough Vcc to operate properly; pulling its Vcc all the way to ground means it is in the region of uncertainty until its Vcc gets to around 1 V. Connecting the front panel reset button directly to the reset line means contact bounce noise will get onto reset which can have some unpleasant effects...