Single Chip Computer - CH552T I2C PCF8574

For more information and technical details please refer to Hackaday project https://hackaday.io/project/194587-single-chip-computer Remote 8-bit I/O expander for I2C‑bus with interrupt. GPIO expanders work like this: you have a board with some number of GPIO but not enough for your project - maybe you need more buttons or LEDs. You could upgrade to a board with massive number of GPIO like the Grand Central, or you could pop on one of these boards. Connect it over I2C and then you can send/receive I2C commands to control the GPIO pins to write and read them. It's going to be slower than direct GPIO access, but maybe that doesn't matter if it takes a millisecond instead of a microsecond. You only need the two I2C pins, and you can even share the I2C port with other sensors and devices. Heck, you can even add more expanders for massive I/O control! First up, its very affordable - who doesn't love that? It has 8 I/O pins Three I2C address select jumpers mean up to 8 expanders to one bus for 64 total GPIO added Each pin can be an input with light pull-up or an output sink IRQ output will automatically alert you when input pins change value This chip does not have a pin direction register. You cannot set the pins to be input or output - instead each pin has two possible states. Basically you can think of it as an open-drain output with a 100K resistor pull-up built in. Option one: Lightly pulled up 'input' - by default it will read as a high logic level, but connecting the GPIO to ground will cause it to read as a low logic level. Option two: Strong 20mA low-driving transistor sink output. This means the output is 'forced' to be low and will always read as a low logic level.