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ADP5589CP-EVALZ Datasheet(PDF) 12 Page - Analog Devices |
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ADP5589CP-EVALZ Datasheet(HTML) 12 Page - Analog Devices |
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12 / 52 page  ADP5589 Data Sheet Rev. B | Page 12 of 52 KEY 32 KEY 32 PRESS KEY 32 RELEASE KEY SCAN EVENT_INT EVENT_INT CLEARED EC[4:0] FIFO FIFO READ 0 0 0 0 0 0 0 0 FIFO 1 0 0 0 32 0 0 0 FIFO 10 1 0 0 0 0 32 0 0 0 Figure 13. Asserting the EVENT_INT Interrupt Key Pad Extension As shown in Figure 11, the keypad can be extended if each row is connected directly to ground by a switch. If the switch placed between R0 and ground is pressed, the whole row is grounded. When the key scanner completes scanning, it normally detects Key 1 to Key 11 as being pressed; however, this unique condi- tion is decoded by the ADP5589, and Key Event 89 is assigned to it. Up to eight more key event assignments are possible, allowing the keypad size to extend up to 96. However, if one of the extended keys is pressed, none of the keys on that row is detectable. Activation of a ground key causes all other keys sharing that row to be undetectable. Ghosting Ghosting is an occurrence where, given certain key press com- binations on a keypad matrix, a false positive reading of an additional key is detected. Ghosting is created when three or more keys are pressed simultaneously on multiple rows or columns (see Figure 14). Key combinations that form a right angle on the keypad matrix can cause ghosting. The solution to ghosting is to select a keypad matrix layout that takes into account three key combinations that are most likely to be pressed together. Multiple keys pressed across one row or across one column do not cause ghosting. Staggering keys so that they do not share a column also avoids ghosting. The most common practice is to place keys that are likely to be pressed together in the same row or column. Some examples of keys that are likely to be pressed together are as follows: The navigation keys in combination with Select. The navigation keys in combination with the space bar. The reset combination keys, such as CTRL + ALT + DEL. COL0 ROW0 ROW1 ROW2 ROW3 PRESS GHOST PRESS PRESS COL1 COL2 Figure 14. COL0-ROW3 is a Ghost Key Due to Short Between ROW0, COL0, COL2 and ROW3 During Key Press FIFO Lock/Unlock The ADP5589 features a lock mode, whereby events are pre- vented from updating the FIFO or the event counter or from generating EVENT_INT interrupts until an unlock event is detected. The lock feature is enabled by setting the LOCK_EN (0x37[0]) bit or, alternatively, by a user programmable key or GPI event (set via EXT_LOCK_EVENT[7:0], Address 0x35). If the lock feature is enabled by the LOCK_EN bit, the LOCK_STAT (0x02[5]) bit is set. If the lock feature is enabled by an external event, then the LOCK_STAT bit is set, and a LOCK_INT interrupt is generated. Unlock events are programmed via the UNLOCK1[7:0] (0x33) and UNLOCK2[7:0] (0x34) registers. Bits[6:0] comprise the even number. Bit 7 determines the active/inactive event (see the UNLOCK1 Register 0x33 (Table 59) and the UNLOCK2 Register 0x34 (Table 60). If the user chooses to use only one unlock event, only the UNLOCK1[7:0] register should be programmed. Unlock events can be key press events (Event 1 to Event 88). Key release events are ignored when the keypad is locked and should not be used as unlock events. GPIs configured to generate FIFO updates can also be used as unlock events (Event 97 to Event 115, either active or inactive). If either UNLOCKx register is programmed with Value 127 (Event 127), this means that any allowable event (key or GPI) is the unlock event. For example, if UNLOCK1[6:0] is programmed with 17, and UNLOCK2[6:0] is programmed with 127, the unlock sequence is Key 17 press followed by any other allowable event. If the first unlock event is detected, partial unlock has occurred. If the next event after the first unlock event is not the second unlock event, then a full lock state is entered again. If the next event after the first unlock event is the second unlock event, then LOCK_STAT is cleared, and a LOCK_INT interrupt is generated. The user can at any stage clear LOCK_EN. This clears the LOCK_STAT bit but does not cause a LOCK_INT interrupt to be generated. |
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