search

prakashlab / octopi-driver-board

Driver electronics for the Octopi and Squid microscope families.
https://squid-imaging.org/
Other
6 stars 5 forks source link

Add pull-up resistors to open-drain logic output pins #17

Closed ethanjli closed 3 years ago

ethanjli commented 3 years ago

As described in the "Step 1" section of https://www.pjrc.com/better-spi-bus-design-in-3-steps/ , we need to ensure that chip-select pins have pull-up resistors so that interference or cross-talk can't spuriously activate an SPI device. If we try to be clever about where we place pull-up resistors to reduce the number of resistors needed (or to make them be part of ODSv1.0.0-BT), we will need to ensure that it works correctly when combined with our SPI CS multiplexing system (which makes demultiplexed CS pins float when they're not connected to DCS; and likewise for DSCS).

ethanjli commented 3 years ago

We should also add pull-up resistors on the address input pins to analog muxes, such as in the backbone. And we should have pull-up resistors on the demultiplexed DSCS lines somewhere, either in PP-T41 or on the DSCS trace of each non-PP-T41 plane. Without those pullups, all the address input pins to the analog muxes are read as low, so DSCS is always connected to SPI_DSCS0.

ethanjli commented 3 years ago

We should add pull-up resistors on all demultiplexed DCS pins in BP-Jmp - probably next to the DCS headers.