ESP8266 Community Forum

I am trying to use the HSPI on the ESP8266 as master. However I it appears that the MISO pin is being driven high by the ESP8266 such that my slave device when driven low can only pull the pin down to ~1.25V, right on the edge of logic high/low thus causing lots of bus errors.

Has anyone else seen this before?

The issue was another part on the bus, specifically an isolated SPI bus adapter which was holding bus high.

The problem was a isolated SPI bus chip. It did not tri-state the MISO when chip select was high.

Moved ESP to different SPI port on micro to work around issue.