觸控設備手勢喚醒的設計思路及其實現
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// example interrupt function where this might be implemented
__interrupt void TimedInterrupt（ void ）
{
uint8 proximity_counts;
uint8 filtered_counts;
....
....
if （ device_status == SLEEP_MODE ）
{
// read one byte from register 0x16
proximity_counts = read_i2c_register（MAX44000_ADDR，0x16，1）;
// weights［QUEUE_SIZE］ contains the filter weights for the FIR filter
// data_queue［QUEUE_SIZE］ is a FIFO queue meant to be the input to the filter
filtered_counts = fir_filter（proximity_counts，weights，data_queue）;
if （filtered_counts 》 WAKEUP_THRESHOLD）
{
device_status = WAKE_MODE;
...
}
else
{
// do whatever it is you need to in sleep mode
...
...
}
}
...
...
}
/**
* fir_filter（）
*
* Implements an FIR filter in the form
* y = w［0］*x［0］ + w［1］*x［1］ + 。。.+ w［QUEUE_SIZE］*x［QUEUE_SIZE］
*
* Arguments：
* uint8 input - newest datapoint taken （that is， x［0］）
* uint8 *weights - w［0］。。.w［QUEUE_SIZE］
* uint8 *queue - the discrete sequence x［0］。。.x［QUEUE_SIZE］
*
* Returns：
* The FIR-filtered output， y
*/
uint8 fir_filter（uint8 input， uint8 *weights， uint8 *queue）
{
uint8 i;
int sum = 0;
// pop first entry in the queue， then
// push new data into the last position
push_into_queue（queue，input）;
// input is now x［0］
for （i=0; i {
sum += weights［i］*queue［i］;
}
return （sum/QUEUE_SIZE）;
}
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