I/O - digital in- and outputs
The module has 16 digital I/Os (CMOS level, non-floating). The input range is 0... 3.3 V. All 16 I/Os have a weak pull-up at approximately 100 kΩ after reset. Remark: The logic is not designed for time-critical operations; i.e. it is not a real-time operating system By using one or more external (max. 7) MCP23017-E (16 I/Os per IC), the total number of I/Os can be expanded up to 128-3. The ports "I/O 1.5 to 1.7" (pins 27 to 29) are redefined and used as serial data lines for the port expander (see application example). This is done by re-soldering 3 resistors (the position of the resistors can be seen in the overview). Because interface is I²C bus, 2 pull-up resistors need to be added (4k7): |
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The maximum power of the MCP23017-E is 700 mW in total. The maximum current load for a single pin is 25 mA, which makes it possible to directly operate a low current LED. If a higher load is required, the I/O current must be amplified with suitable circuitry, e.g. through an external transistor. More details at Electrical characteristics
The overview of the software commands for the I/Os can be found under the chapter 'I/O Port'.