https://devzone.nordicsemi.com/f/nordic-q-a/4486/spi-slave-miso-high-until-buffers-setI am working with the nRF51822 S110 and having trouble implementing SPI. In other devices&#39; SPI protocols, MISO can be held high until the device is ready to transmit data. I want to bring MISO high and then set it low once the SPI_SLAVE_BUFFERS_SET_DONEen-USTelligent Community 13Tue, 18 Nov 2014 13:53:48 GMThttps://devzone.nordicsemi.com/thread/15907?ContentTypeID=1Tue, 18 Nov 2014 13:53:48 GMT137ad170-7792-4731-bb38-c0d22fbe4515:1d32f020-7dce-4d84-a158-87f07dccb227Stefan Birnir Sverrisson<p>Hi</p> <p>Usually we would recommend to add the fifth line, which the SPI slave uses to signal the master that it is ready to send data, but I hear that no extra line is available in your case.</p> <ul> <li>I guess you could manually write 0xFFFFFFFF to the PSELMISO register to momentarily unconfigure the MISO pin</li> <li>Manually set the MISO pin high when SPIS has data to send</li> <li>When the master sets the CSN line low to start a SPI transaction, reconfigure the MISO pin by writing the the PSELMISO</li> <li>Make sure the master will wait for an adequate time so the nRF51822 has time to reconfigure the PSELMISO before SPI master will start to clock out data.</li> </ul> <p>The use of MISO line would only work if there are no other SPI slaves on the SPI bus.</p><div style="clear:both;"></div>