Mobile I/O Expander and QWERTY Keypad Controller
The ADP5588 is an I/O port expander and keypad matrix designed for QWERTY type phones that require a large keypad matrix and expanded I/O lines. I/O expander ICs are used in mobile platforms as a solution to the limited number of GPIOs available in the main processor.
In its small 4 mm × 4 mm package, the ADP5588 contains enough power to handle all key scanning and decoding and flag the processor of key presses and releases via the I2C® interface and interrupt. It frees the main microprocessor from having to monitor the keypad, thereby minimizing current drain and increasing processor bandwidth. It is also equipped with a buffer/FIFO and key event counter to handle and keep track of up to 10 unprocessed key or GPI events with overflow wrap and interrupt capability.
The ADP5588 has a keylock capability with an option to trigger or not trigger an interrupt at key presses and releases. All communication to the main processor is done using one interrupt line and two I2C-compatible interface lines. The ADP5588 can be configured to have a keypad matrix of up to 8 rows × 10 columns (a maximum of 80 keys).
When used for smaller keypad matrices, unused row and column pins can be reconfigured to act as general-purpose inputs, outputs, or light sensor inputs. R0, R1, R2, R3, R4, R5, R6, and R7 denote the row pins of the matrix, while C0, C1, C2, C3, C4, C5, C6, C7, C8, and C9 denote the column pins. At power-up, all rows and columns default as GPIs and must be programmed to function as part of the keypad matrix, GPOs, or light sensor inputs. In addition to keypad and GPIO functionalities, C8 and C9 can also be configured as light sensor inputs.
When configured as keypad lines, the function of the C8 and C9 lines is straightforward: the control interface disconnects these lines from the comparator inputs, disables the light sensor comparator, and connects them to the keypad columns of the keypad matrix. When used as light sensor comparator inputs, the control interface disconnects these pins from the keypad, enables the comparators, and connects these lines to the comparator inputs. Two external capacitors (0.1 μF) are required when these pins are configured as light sensor inputs. When used as GPIOs, these pins are removed from the keypad and the light sensor interface, and the light sensor comparators are disabled, along with the logic for the sensors.Applications
- Keypad and I/O expander designed for QWERTY type phones that require a large keypad matrix
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
The demonstration board assembly is powered either via J10 or the USB port and comes with a free graphical user interface (GUI) to exercise the ADP5588 features. In addition to the keypad switches, the motherboard also has 18 GPO LED indicators (D1 through D11, D22 through D27, and D30), power status LEDs (D19 and D21), a 2.7 V regulator, a 3.3 V regulator, and jumpers (J1 through J8 and J13 through J22) to configure the GPIOs as GPIs, GPOs, or keypad lines. The motherboard is equipped with jumpers (LK8 and LK10) to configure the board to use either external regulated voltages via J10 or the on-board regulators when plugged into the USB port. When using the USB port as the power source, place jumpers across Pin 1 and Pin 2 of LK8 and LK10. When using external voltages, place jumpers across Pin 2 and Pin 3 of LK8 and LK10. VCC (Pin 3 of J10) should be 1.8 V to 3.0 V, and VBOARD (Pin 1 of J10) should be 3.3 V.
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