mum speed is approximately 450kHz.</p>
   <h4>SPI</h4>
   <p>The ESP8266 has one SPI connection available to the user, referred to as HSPI. It uses GPIO14 as CLK, 12 as MISO, 13 as MOSI and 15 as Slave Select (SS). It can be used in both Slave and Master mode (in software).</p>
   <h3>GPIO overview</h3>
   <table style="box-sizing: border-box;border-spacing: 0px;border-collapse: collapse;margin-top: 0px;margin-bottom: 16px;display: block; overflow: auto; color: rgb(51, 51, 51);font-family: -apple-system, Bl