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接触式电容键盘参考图
[COLOR=blue]//******************************************************************************
// MSP430F20x3 Demo - Capacitive Touch Sensing 4-Key Demo
// Description: This demo implements a 4-key capacitive touch detection.
// The LED indicates the key which is pressed through four different levels of
// brightness. Key#1 -> 100%, Key#2 -> 75%, Key#3 -> 50%, Key#4 -> 25%.
// A calibration process is implemented to accommodate for possible variations
// in VLO frequency. Normal operating mode is LPM3.
//
// ACLK = VLO ~ 12kHz, MCLK = Calibrated 8MHz / 4 = 2MHz,
// SMCLK = Calibrated 8MHz
//
// MSP430F20x3
// -----------------
// /|\| XIN|-
// | | |
// --|RST XOUT|-
// | |
// | P1.0|---->LED
// | | ####
// | P1.2|----+--------#### Sensor#4
// | | # ####
// | | # R=5.1M
// | | # ####
// | P1.3|----+--------#### Sensor#3
// | | ####
// | |
// | | ####
// | P1.4|----+--------#### Sensor#2
// | | # ####
// | | # R=5.1M
// | | # ####
// | P1.5|----+--------#### Sensor#1
// | | ####
//
// Zack Albus
// Texas Instruments Inc.
// June 2007
// Built with IAR Embedded Workbench Version: 3.42A
//******************************************************************************[/COLOR]
#include "msp430x20x3.h"
// Define User Configuration values
// Sensor settings
#define Num_Sen 4 // Defines number of sensors
#define S_4 (0x04) // Sensor 4 P1.2
#define S_3 (0x08) // Sensor 3 P1.3
#define S_2 (0x10) // Sensor 2 P1.4
#define S_1 (0x20) // Sensor 1 P1.5
#define LED (0x01) // P1.0
#define min_KEY_lvl 30 // Defines the min key level threshold usable
#define Sample_Rate 20 // Defines #/sec all sensors are sampled
#define DCO_clks_per_sec 8000000 // Number of DCO clocks per second: 2MHz
// Changes with DCO freq selected!
#define DCO_clks_per_sample (DCO_clks_per_sec/Sample_Rate)/8
// Clocks per sample cycle /8
// /8 is allows integer usage
// will be *8 in the final calcs
#define LED_pulses_per_sample 5 // Defines LED pulses during each sample
// -number of TACCR0 ints per sample
#define Key_1_on_time 1 // Defines Key 4 % on
#define Key_2_on_time 10 // Defines Key 3 % on
#define Key_3_on_time 25 // Defines Key 2 % on
#define Key_4_on_time 90 // Defines Key 1 % on
// Global variables for sensing
unsigned int dco_clks_per_vlo; // Variable used for VLO freq measurement
unsigned int vlo_clks_per_sample; // Variable that determines vlo clocks per sample
// vlo_clks_per_sample = DCO_clks_per_sample/dco_clks_per_vlo*8
unsigned int vlo_clks_per_LED_pulse; // Variable that determines vlo clocks per LED pulse
unsigned int LED_on_time[Num_Sen]; // Stores calculated TACCR1 value for each
// key separately. Calculated from
// Key_x_on_time*vlo_clks_per_LED_pulse/100
// Misc Globals
unsigned int base_cnt[Num_Sen];
unsigned int meas_cnt[Num_Sen];
int delta_cnt[Num_Sen];
unsigned char key_press[Num_Sen];
char key_pressed, key_loc, no_key, key_loc_old, key_time_out;
char cycles;
unsigned int timer_count;
unsigned int KEY_lvl = 100; // Defines the min count for a "key press"
// System Routines
void Init_Timings_Consts(void); // Use VLO freq to determine TA values
void measure_count(void); // Measures each capacitive sensor
extern unsigned int Measure_VLO_SW(void); // External function to measure
// speed of the VLO
// (implemented in Measure_VLO_SW.s43)
// Main Function
void main(void)
{
unsigned int i,j;
int temp;
// Configure clock system
WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer
dco_clks_per_vlo = Measure_VLO_SW(); // Determine VLO freq for usage
BCSCTL2 |= DIVM_2; // MCLK / 4
BCSCTL1 = CALBC1_8MHZ; // Set DCO to 8MHz
DCOCTL = CALDCO_8MHZ; // MCLK = 8/4 = 2MHz
BCSCTL3 |= LFXT1S_2; // LFXT1 = VLO
// Configure GPIOs
P1OUT = 0x00; // P1.x = 0
P1DIR = 0xFF; // P1.x = output
P2OUT = 0x00;
P2DIR = 0xFF; // P2.x = output
P2SEL = 0x00; // No XTAL
__enable_interrupt(); // Enable interrupts
Init_Timings_Consts();
measure_count(); // Establish an initial baseline capacitance
for (i = 0; i<Num_Sen; i++)
base_cnt = meas_cnt;
for (i=15; i>0; i--) // Repeat and average base measurement
{
measure_count();
for (j = 0; j<Num_Sen; j++)
base_cnt[j] = (meas_cnt[j]+base_cnt[j])/2;
}
no_key = 0;
// Main loop starts here
while (1)
{
key_pressed = 0; // Assume no keys are pressed
measure_count(); // Measure all sensors
for (i = 0; i<Num_Sen; i++)
{
delta_cnt = meas_cnt - base_cnt; // Calculate delta: c_change
// Handle baseline measurment for a base C decrease
if (delta_cnt < 0) // If negative: result decreased
{ // below baseline, i.e. cap decreased
base_cnt = (base_cnt+meas_cnt) >> 1; // Re-average baseline down quickly
delta_cnt = 0; // Zero out delta for position determination
}
if (delta_cnt > KEY_lvl) // Determine if each key is pressed per a preset threshold
{
key_press = 1; // Specific key pressed
key_pressed = 1; // Any key pressed
key_loc = i;
}
else
key_press = 0;
}
// Handle baseline measurement for a base C increase
if (!key_pressed) // Only adjust baseline up if no keys are touched
{
key_time_out = Sample_Rate*3; // Reset key time out duration
for (i = 0; i<Num_Sen; i++)
base_cnt = base_cnt + 1; // Adjust baseline up, should be slow to
} // accomodate for genuine changes in sensor C
else // Key pressed
{
if (key_loc_old == key_loc) // same key pressed?
key_time_out--;
else
key_time_out = Sample_Rate*3; // Reset key time out duration
key_loc_old = key_loc;
if (key_time_out == 0) // After time-out, re-init base and key level
WDTCTL = WDTHOLD; // FORCE RESET
}
// Dynamically adjust key thresholds
if (key_pressed && (delta_cnt[key_loc]>>2 > KEY_lvl))
{
temp = delta_cnt[key_loc]>>2;
temp = temp + KEY_lvl;
temp = temp>>1;
KEY_lvl = temp; // Average result
}
else if (!key_pressed)
{
for (i = 0; i<Num_Sen; i++)
{
if(delta_cnt > min_KEY_lvl)
{
temp = delta_cnt>>1; // Means min key level threshold = %50 of delta measured
temp = temp + KEY_lvl; // or = min_KEY_lvl/2
temp = temp>>1;
KEY_lvl = temp; // Average result
break;
}
}
}
if (key_pressed) // Pulse LED and use defined sample rate
{
no_key = Sample_Rate*3; // Reset ~3 sec delay until slower sample rate is used
cycles = LED_pulses_per_sample; // Re-set LED pulse counter
TACCTL0 = CCIE;
TACCR0 = vlo_clks_per_LED_pulse; // Load LED pulse period
TACCTL1 = CCIE;
TACCR1 = LED_on_time[key_loc]; // Load LED pulse duty cycle
P1OUT |= LED; // Turn on LED
}
else // No key is pressed...
{
if (no_key == 0) // ...~3 sec timeout expired: no key press in ~3secs...
{
cycles = 1; // Adjust cycles for only one TA delay
TACCTL0 = CCIE;
TACCR0 = vlo_clks_per_LED_pulse*LED_pulses_per_sample*5; // Low sample rate to: sample_rate/5 SPS
}
else // ... still within 3 secs of last detected key press...
{
no_key--; // Decrement delay
cycles = LED_pulses_per_sample; // Maintain sample_rate SPS, without LED
TACCTL0 = CCIE;
TACCR0 = vlo_clks_per_LED_pulse;
}
P1OUT ^= BIT6; // Toggle P1.6 (for debug only)
}
TACTL = TACLR + TASSEL_1 + MC_1; // ACLK = VLO, up mode
LPM3;
}
} // End Main
// Measure count result (capacitance) of each sensor
// Routine setup for four sensors, not dependent on Num_Sen value!
void measure_count(void)
{
unsigned char i;
char active_key;
TACTL = TASSEL_2+MC_2; // SMCLK, cont mode
for (i = 0; i<Num_Sen; i++)
{
active_key = 1 << i+2; // define bit location of active key
//******************************************************************************
// Negative cycle
//******************************************************************************
P1OUT &=~(S_1+S_2+S_3+S_4); // everything is low
// Take the active key high to charge the pad
P1OUT |= active_key;
// Allow a short time for the hard pull high to really charge the pad
__no_operation();
__no_operation();
__no_operation();
// Enable interrupts (edge set to low going trigger)
// set the active key to input (was output high), and start the
// timed discharge of the pad.
P1IES |= active_key; //-ve edge trigger
P1IE |= active_key;
P1DIR &= ~active_key;
// Take a snaphot of the timer...
timer_count = TAR;
LPM0;
// Return the key to the driven low state, to contribute to the "ground"
// area around the next key to be scanned.
P1IE &= ~active_key; // disable active key interrupt
P1OUT &= ~active_key; // switch active key to low to discharge the key
P1DIR |= active_key; // switch active key to output low to save power
meas_cnt= timer_count;
//****************************************************************************
// Positive Cycle
//****************************************************************************
P1OUT |= (S_1+S_2+S_3+S_4); // everything is high
// Take the active key low to discharge the pad
P1OUT &= ~active_key;
// Allow a short time for the hard pull low to really discharge the pad
__no_operation();
__no_operation();
__no_operation();
// Enable interrupts (edge set to high going trigger)
// set the active key to input (was output low), and start the
// timed discharge of the pad.
P1IES &= ~active_key; //+ve edge trigger
P1IE |= active_key;
P1DIR &= ~active_key;
// Take a snaphot of the timer...
timer_count = TAR;
LPM0;
// Return the key to the driven low state, to contribute to the "ground"
// area around the next key to be scanned.
P1IE &= ~active_key; // disable active key interrupt
P1OUT &= ~active_key; // switch active key to low to discharge the key
P1DIR |= active_key; // switch active key to output low to save power
P1OUT &=~(S_1+S_2+S_3+S_4); // everything is low
meas_cnt = (meas_cnt + timer_count) >> 1; // Average the 2 measurements
}
TACTL = TACLR; // Stop the timer
}
void Init_Timings_Consts(void)
{
// dco_clks_per_vlo = dco_clks_per_vlo << 1; // x2 for 2MHz DCO
// dco_clks_per_vlo = dco_clks_per_vlo << 2; // x4 for 4MHz DCO
dco_clks_per_vlo = dco_clks_per_vlo << 3; // x8 for 8MHz DCO
// dco_clks_per_vlo = dco_clks_per_vlo << 4; // x16 for 16MHz DCO
vlo_clks_per_sample = DCO_clks_per_sample/dco_clks_per_vlo*8;
vlo_clks_per_LED_pulse = vlo_clks_per_sample/LED_pulses_per_sample;
LED_on_time[0] = Key_1_on_time*vlo_clks_per_LED_pulse/100;
if(LED_on_time[0] == 0)
LED_on_time[0] = 1;
LED_on_time[1] = Key_2_on_time*vlo_clks_per_LED_pulse/100;
LED_on_time[2] = Key_3_on_time*vlo_clks_per_LED_pulse/100;
LED_on_time[3] = Key_4_on_time*vlo_clks_per_LED_pulse/100;
}
// Port 1 interrupt service routine
#pragma vector=PORT1_VECTOR
__interrupt void port_1_interrupt(void)
{
P1IFG = 0; // clear flag
timer_count = TAR - timer_count; // find the charge/discharge time
LPM0_EXIT; // Exit LPM0 on reti
}
// Timer_A0 interrupt service routine
#pragma vector=TIMERA0_VECTOR
__interrupt void Timer_A0 (void)
{
cycles--;
if (cycles > 0)
{
if (key_pressed)
P1OUT |= LED; // LED on for TACCR1 time of TA period
}
else
{ TACTL = TACLR;
TACCTL0 = 0; // interrupt disabled
TACCTL1 = 0; // interrupt disabled
LPM3_EXIT; // Exit LPM3 on reti
}
}
// Timer_A1 interrupt service routine
#pragma vector=TIMERA1_VECTOR
__interrupt void Timer_A1 (void)
{
TACCTL1 &= ~CCIFG; // Clear the flag
P1OUT &= ~LED; // LED off for rest of TA period
}
//暂时为大家提供的是TI原文源代码，有兴趣的网友可以将其注解翻译成中文出来分享给大家参考。
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