There are lots of MCUs with many GPIOs, but apparently, they’re never enough. Wanna 40 more?
40 more GPIOs might be a very welcome addition to your next system design with a low-end MCU or with a Raspberry Pi-based system since, as to date, there are not so many GPIOs in Raspberry Foundation’s boards (if you let alone the Compute module Expansion board for industrial applications).
The IC we’re taking advantage of on this board is the PCA9698 from NXP, an advanced IO port expander that can be fully controlled with any I2C capable microcontroller and can be configured to operate its pins either as open-collector or totem-pole (Datasheet page 13 of 48).
Be aware that this configuration cannot change any single pin behavior without affecting others (actually there’s a little trick to handle some of them in pairs), it changes the whole port into which your desired pin is placed, thus in case you want to operate with both totem-pole and open-collector GPIOs, be sure to use pins assigned to different banks (meaning different initial number on this PCB).
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Nadim Conti 