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MPR081EJ Datasheet(PDF) 10 Page - Freescale Semiconductor, Inc |
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MPR081EJ Datasheet(HTML) 10 Page - Freescale Semiconductor, Inc |
10 / 22 page MPR081 Sensors 10 Freescale Semiconductor INTERRUPT CONTROLLER AND IRQ OUTPUT The IRQ pin is an open-drain, latching interrupt output which automatically alerts changes to a user-configurable combination of keyswitches and/or touch pads. IRQ requires an external pullup resistor, which can be connected to any voltage up to VDD. When set active low, IRQ is reset high immediately after the slave address acknowledge of the first subsequent read or write access to the MPR081. If an interrupt causing event occurs during an I2C transmission to the MPR081, the interrupt is not asserted. Instead, it is asserted after the I2C transmission is terminated (by a STOP condition or a repeated START condition), but only if the affected registers were not read during the I2C communication. This avoids unnecessary assertion of the interrupt. An interrupt can be enabled for: • Initial touch (when rotary condition goes from untouched to touched) • Touch release ROTARY TOUCH INTERFACE The rotary interface has to distinguish touch status through varying user conditions (different finger sizes in bare hands or gloves) and environmental conditions (electrical and RF noise, sensor contamination with dirt or moisture). The rotary circuitry reports status as one of five conditions: rotary untouched, and rotary touched in one of four positions. Normally, the rotary is only touched in one position, ideally near the middle of one of the four pads. If a touch occurs more or less between pads, either the nearest pad will be given or the touch will be ignored depending on exact touch position and finger size. The rotary circuitry interprets multiple simultaneous rotary touches (more than one rotary pad being touched at the same time) as best it can. The scenarios are as follows: 1. Two rotary pads touched at the same time • If the two touched rotary pads are both full or both split, the touches are ignored until one is removed • If one touched rotary pad is full and the other touched rotary pad is split, the full pad position will be reported. • If the full pad touch is removed first, the split pad position now will be reported. 2. First one rotary pad is touched and held, then a second rotary pad is touched and held. • The second touch will be ignored and the first touch will continue to be active. If the first touch is removed while the second pad is still being touched, then the second pad becomes the only touched pad and so is reported. Table 8. Register Address Map Register Register Address Register Address Auto-Increment Address Auto-Increment Loop D15 D14 D13 D12 D11 D10 D9 D8 FIFO 0 0 0 0 0 0 0 0 0x00 0x00 FIFO Fault 0 0 0 0 0 0 0 1 0x01 0x02 Rotary Status 0 0 0 0 0 0 1 0 0x02 0x00 FIFO Rotary Configuration 0 0 0 0 0 0 1 1 0x03 0x04 Sensitivity 0 0 0 0 0 1 0 1 0x04 0x05 Master Tick Counter 0 0 0 0 0 1 1 0 0x05 0x06 Touch Acquisition Sample Rate 0 0 0 0 0 1 1 1 0x06 0x07 Sounder 0 0 0 0 1 0 0 0 0x07 0x08 Sleep Period 0 0 0 0 1 0 0 1 0x08 0x09 Configuration 0 0 0 0 1 0 1 0 0x09 0x00 FIFO Table 9. Power-Up Register Configurations Register Function Power-Up Condition Register Address Register Data D7 D6 D5 D4 D3 D2 D1 D0 FIFO FIFO is empty 0x00 0 0 0 0 0 0 0 0 Fault No faults 0x01 0 0 0 0 0 0 0 0 Rotary Status Rotary is untouched 0x02 0 0 0 0 0 0 0 0 Rotary Configuration Rotary is enabled, without interrupts, with sounder enabled 0x03 1 0 0 0 0 0 0 1 Sensitivity Level is very sensitive 0x04 0 0 0 0 0 0 0 0 Master Tick Counter Master tick period is 10 ms 0x05 0 0 0 0 0 1 0 1 Touch Acquisition Sample Rate Touch acquisition sample rate is 5 master tick periods 0x06 0 0 0 0 0 1 0 0 Sounder Sounder is globally enabled, 10 ms of 1 kHz 0x07 0 0 0 0 0 0 0 1 Sleep Period Sleep mode is disabled 0x08 0 0 0 0 0 0 0 0 Configuration Shutdown mode. IRQ is disabled 0x09 0 0 0 0 0 0 0 0 |
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