HOW DOES IT WORK?

Expand 9 Click as its foundation uses the SX1509QB, a 16-channel lowest voltage level shifting GPIO expander from Semtech Corporation. The expander devices, like this one, can provide additional control and monitoring when the MCU has insufficient I/O ports or in systems where serial communication and control from a remote location are advantageous. The SX1509QB has a built-in level shifting feature making it highly flexible in power supply systems where communication between incompatible I/O voltages is required, thus eliminating extra level translating circuits.

The SX1509QB features a fully programmable LED driver with an internal oscillator for enhanced lighting control such as intensity (via 256-step PWM), blinking, and breathing (fade In/Out) which makes them highly versatile for a wide range of LED applications. Also, keypad applications are supported with an on-chip scanning engine enabling continuous keypad monitoring up to 64 keys (8x8 matrix) without any additional host interaction reducing bus activity.

Expand 9 Click communicates with MCU using the standard I2C 2-Wire interface to read data and configure settings, supporting a Fast Mode operation up to 400kHz. The selection of the I2C slave address is also possible, using the ADD pin routed to the AN pin of the mikroBUS™ socket. This way, the SX1509QB provides the opportunity of the two possible different I2C addresses by setting ADD pin to an appropriate logic state. In addition to selecting a Slave address, the SX1509QB can generate mask-programmable interrupts based on a falling/rising edge of any of its GPIO lines. A dedicated interrupt pin, routed to the INT pin of the mikroBUS™ socket, indicates to a host controller that a state change occurred on one or more of the expand lines, while the RST pin of the mikroBUS™ socket represents a Reset feature used to reset the chip at any time.

Each GPIO on I/O Expander channels is programmable via a bank of 8-bit configuration registers, including data, direction, pull-up/pull-down, interrupt mask, and interrupt registers. The user is also given an option of selecting the expander port supply voltage, which is realized by two onboard switches labeled as VCCA and VCCB, allowing one to choose between 3.3V and 1.8V. To obtain 1.8V, a small LDO regulator is added, AP2112 from Dialog Incorporated, to provide 1.8V out of mikroBUS™ power rail.

This Click board™ can be operated only with a 3.3V logic voltage level. The board must perform appropriate logic voltage level conversion before use with MCUs with different logic levels. However, the Click board™ comes equipped with a library containing functions and an example code that can be used, as a reference, for further development.