1  /* Teensyduino Core Library
 2   * http://www.pjrc.com/teensy/
 3   * Copyright (c) 2013 PJRC.COM, LLC.
 4   *
 5   * Permission is hereby granted, free of charge, to any person obtaining
 6   * a copy of this software and associated documentation files (the
 7   * "Software"), to deal in the Software without restriction, including
 8   * without limitation the rights to use, copy, modify, merge, publish,
 9   * distribute, sublicense, and/or sell copies of the Software, and to
10   * permit persons to whom the Software is furnished to do so, subject to
11   * the following conditions:
12   *
13   * 1. The above copyright notice and this permission notice shall be 
14   * included in all copies or substantial portions of the Software.
15   *
16   * 2. If the Software is incorporated into a build system that allows 
17   * selection among a list of target devices, then similar target
18   * devices manufactured by PJRC.COM must be included in the list of
19   * target devices and selectable in the same manner.
20   *
21   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
22   * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
23   * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
24   * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
25   * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
26   * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
27   * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
28   * SOFTWARE.
29   */
30  
31  #include "core_pins.h"
32  //#include "HardwareSerial.h"
33  
34  static const uint8_t pin2tsi[] = {
35  //0    1    2    3    4    5    6    7    8    9
36    9,  10, 255, 255, 255, 255, 255, 255, 255, 255,
37  255, 255, 255, 255, 255,  13,   0,   6,   8,   7,
38  255, 255,  14,  15, 255,  12, 255, 255, 255, 255,
39  255, 255,  11,   5
40  };
41  
42  // These settings give approx 0.02 pF sensitivity and 1200 pF range
43  // Lower current, higher number of scans, and higher prescaler
44  // increase sensitivity, but the trade-off is longer measurement
45  // time and decreased range.
46  #define CURRENT   2 // 0 to 15 - current to use, value is 2*(current+1)
47  #define NSCAN     9 // number of times to scan, 0 to 31, value is nscan+1
48  #define PRESCALE  2 // prescaler, 0 to 7 - value is 2^(prescaler+1)
49  
50  
51  // output is approx pF * 50
52  // time to measure 33 pF is approx 0.25 ms
53  // time to measure 1000 pF is approx 4.5 ms
54  
55  int touchRead(uint8_t pin)
56  {
57  	uint32_t ch;
58  
59  	if (pin >= NUM_DIGITAL_PINS) return 0;
60  	ch = pin2tsi[pin];
61  	if (ch == 255) return 0;
62  
63  	*portConfigRegister(pin) = PORT_PCR_MUX(0);
64  	SIM_SCGC5 |= SIM_SCGC5_TSI;
65  	TSI0_GENCS = 0;
66  	TSI0_PEN = (1 << ch);
67  	TSI0_SCANC = TSI_SCANC_REFCHRG(3) | TSI_SCANC_EXTCHRG(CURRENT);
68  	TSI0_GENCS = TSI_GENCS_NSCN(NSCAN) | TSI_GENCS_PS(PRESCALE) | TSI_GENCS_TSIEN | TSI_GENCS_SWTS;
69  	delayMicroseconds(10);
70  	while (TSI0_GENCS & TSI_GENCS_SCNIP) ; // wait
71  	delayMicroseconds(1);
72  	return *((volatile uint16_t *)(&TSI0_CNTR1) + ch);
73  }
74  
75  
76  
77