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Pin 3 Mode Setting. This is a digital input used to determine if the program will enter normal mode or the test mode. The line is read after power up, and the code runs the mode that is selected. High=normal mode, Low=test mode.

Pin 4 Sample Rate Selection. This is a digital input used to determine whether the sample rate should be 11025 Hz or 8000 Hz. High=, Low=. This setting only has an effect during normal operating mode, and it can be changed at any time during operation.

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    \$\begingroup\$ These are simply pull-up resistors. These can have a range of values. But looking at other pullups in the same schematic we can see that the author would probably use 10K. \$\endgroup\$
    – Eugene Sh.
    Jan 15, 2018 at 19:59

1 Answer 1


It looks like an oversight that the value was left out, since values are shown for other resistors in the schematic. If you have the full documentation, you should be able to find the value (and preferred vendor and part number) in the bill of materials (BOM) for the design.

In any case, if you don't have the BOM, the value at this location is not critical. I'd use 10k to match the other pull-ups in the design, or perhaps 47k if power is critical.

  • \$\begingroup\$ Thanks for the quick answers! googles "pull-up resistors" \$\endgroup\$ Jan 15, 2018 at 20:03

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