IOError: [Errno 9] Bad file descriptor (Multi-threaded SPI Issue)/members-area/personalblogs/b/blog/posts/ioerror-errno-9-bad-file-descriptor-multi-threaded-spi-issueIn my case this error was occurring due to multi-threaded accesses to a MCP23S17 I/O expander and an MCP3008 ADC analog to digital converter. Errors looked like: File &quot;/home/pi/RWPi/PDALib.py&quot;, line 324, in writeDior = spi.xfer([0x40,reg,v...en-USTelligent Community 12RE: IOError: [Errno 9] Bad file descriptor (Multi-threaded SPI Issue)https://community.element14.com/members-area/personalblogs/b/blog/posts/ioerror-errno-9-bad-file-descriptor-multi-threaded-spi-issueMon, 04 Jul 2016 21:12:29 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:3e51944d-6837-46ae-b16e-c1346bb26f7bclem570<p>So the events were overlapping and therefore not being serviced soon enough. Lessons learned.</p><p>C</p><img src="https://community.element14.com/aggbug?PostID=21761&AppID=293&AppType=Weblog&ContentType=0" width="1" height="1">