This page: https://learn.sparkfun.com/tutorials/py … alog-input
Says:
Connect MOSI (GPIO10, pin 19) to Din on the MCP3002
Connect MISO (GPIO9, pin 21) to Dout on the MCP3002
Connect SCLK (GPIO11, pin 21) to CLK on the MCP3002
The SCLK is being connected to “pin 21”, which is the same pin that is being used by MISO (GPIO9, pin 21). This is incorrect.
SCLK(SPIO11) should be connected to pin 23 (GPIO11, pin 23).