How to increase GPIO on any STM32 MCU?

[parth kothiya]

I want to design PLC using STM32 MCU so for that I need to extend its GPIO pins how can i do this?

Adding another MCU or shift registers any other ideas?

Main cpu having MCU and another io modules added is communicate with ​main cpu using protocol like SPI , I2C ..

[Pavel A.]

Use GPIO expanders on I2C or SPI.

[Javier1]

How fast and how many GPIOS do you need.

Shift registers are the fastest and cheapest of them all.(careful with the transients)

They need 3 GPIOS to be driven (clock, latch ,data) and you could daisy chain them.

I would use the SPI/i2c options only if i was already using the spi/i2c and i culdnt spare gpios to drive the shift registers

[Muhammed Güler]

Additional ICs on a single card often cost more than a larger model of the same processor. For additional modules, you can use a circuit with an SPI/I2C IO expander IC, or you can design a circuit that can be configured for different features with a MCU.

I would like to remind you that it is more difficult to debug designs with multiple MCUs.