10/21/2023 0 Comments Arduino wire library send floatIf the pin is driven HIGH by the MCU, a strong pull-up is turned on for a short time to pull the pin HIGH quickly, and then the weak 100uA pull-up is turned back on to keep the pin HIGH. A strong pull-down is turned on and stays on to keep the pin pulled LOW. If used as outputs, they can be driven LOW by the MCU by writing a LOW to that pin. They will read as HIGH if there is no input or if the pin is being driven HIGH by an external signal but can be driven LOW by an external signal that can easily override the weak pull-up. When using the pins as inputs, the pins are set to HIGH by the MCU, which turns on a weak 100 uA internal pull-up to Vcc. As shipped, these jumpers are all set to the ‘-‘ side, which is ground or LOW, as shown in the picture. There are three address jumps (A0-A2) that determine which I2C address to use. The module has an easy-to-use I2C interface that can be configured to use any one of eight different I2C addresses if you want to use multiple modules in the same system or if you run into an address conflict with another device. It provides 8 additional digital I/O lines, which are easily expandable up to 64. The PCF8574 is one of the more popular methods of adding lines as it uses the I2C bus that requires only 2 lines on the MCU. I2C interface with jumper adjustable addressesĪ common requirement when working with MCUs is the need to add more digital I/O than the device supports natively.Loop-thru feature allows expansion of up to 8 modules / 64 data lines.Key features of PCF8574 I2C I/O expansion Arduino manages 4 buttons and 4 LEDs at the same time.STM32 manage 4 buttons and 4 LEDs at the same time.Esp32 LEDs blink using a secondary i2c channel. Key features of PCF8574 I2C I/O expansion.
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