Looking at the sample, it calls adc.begin() however both begin prototypes take parameters. What function does this call ?

Hi !

I get a fatal error with this comment :

"...libraries\Adafruit_MCP3008-master/Adafruit_MCP3008.h:22:32: fatal error: Adafruit_SPIDevice.h: No such file or directory"

??
thanks in advance

:)

Thank you for this library, works perfectly ; however, I would like to report an observation which seems to allow an improvement.

Indeed, I was initially very disappointed by the measurement speeds.
I compare below 4x6 measurement cycles:

• arduino NANO ADC pins : 600 microseconds
• ESP32 ADC1 pins : 1100 us (!)
• MCP3008 (on ESP32) : 800 us

What I wanted to point out is that by only changing the SPI clock => spiCLK=8000000 ;
I get in combination with the ESP32 a much better time of 330us. Without noticing that measures are less accurate.

(BUT MAYBE IS THERE A DISADVANTAGE I DIDN'T (yet) DETECT ??)

Convert to BusIO usage:
https://github.com/adafruit/Adafruit_BusIO

The code which reads a value from the ADC via a software SPI port seems to be missing a bit. The maximum value reported is 512. Only 16 bits (Including the dummy bits used to read back the result) are sent to the ADC, but the datasheet calls for one more - The hardware SPI version sends a total of 24 bits.
https://github.com/adafruit/Adafruit_MCP3008/blob/master/Adafruit_MCP3008.cpp#L150-L167

• Arduino board: ESP32 (TTGO T-Display)

• Arduino IDE version (found in Arduino -> About Arduino menu): 1.8.12

• List the steps to reproduce the problem below (if possible attach a sketch or
  copy the sketch code in too):

1. Use the library with the software SPI constructor
2. Read the ADC on any channel
3. The result will be between 0 and 511

Here's a version which I used to test the theory that it is just missing the last bit - I hacked in the last bit after the loop:

    uint16_t outBuffer, inBuffer = 0;

    digitalWrite(cs, LOW);

    // 5 command bits + 1 null bit + 10 data bits = 16 bits
    outBuffer = command << 8;
    for (int c = 0; c < 16; c++) {
      digitalWrite(mosi, (outBuffer >> (15 - c)) & 0x01);
      digitalWrite(sck, HIGH);
      digitalWrite(sck, LOW);
      inBuffer <<= 1;
      if (digitalRead(miso))
        inBuffer |= 0x01;
    }

    digitalWrite(mosi, 0x00);
    digitalWrite(sck, HIGH);
    digitalWrite(sck, LOW);

    inBuffer <<= 1;
    if (digitalRead(miso))
      inBuffer |= 0x01;

    digitalWrite(cs, HIGH);

    return inBuffer & 0x3FF;