common/chibios/sleep_led.c

   1 #include "ch.h"
   2 #include "hal.h"
   3
   4 #include "led.h"
   5 #include "sleep_led.h"
   6
   7 #if defined(KL2x) || defined(K20x) /* platform selection: familiar Kinetis chips */
   8 /* All right, we go the "software" way: LP timer, toggle LED in interrupt.
   9  * Based on hasu's code for AVRs.
  10  */
  11
  12 /* Breathing Sleep LED brighness(PWM On period) table
  13  * (64[steps] * 4[duration]) / 64[PWM periods/s] = 4 second breath cycle
  14  *
  15  * http://www.wolframalpha.com/input/?i=%28sin%28+x%2F64*pi%29**8+*+255%2C+x%3D0+to+63
  16  * (0..63).each {|x| p ((sin(x/64.0*PI)**8)*255).to_i }
  17  */
  18 static const uint8_t breathing_table[64] = {
  19 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 4, 6, 10,
  20 15, 23, 32, 44, 58, 74, 93, 113, 135, 157, 179, 199, 218, 233, 245, 252,
  21 255, 252, 245, 233, 218, 199, 179, 157, 135, 113, 93, 74, 58, 44, 32, 23,
  22 15, 10, 6, 4, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
  23 };
  24
  25 /* Low Power Timer interrupt handler */
  26 OSAL_IRQ_HANDLER(KINETIS_LPTMR0_IRQ_VECTOR) {
  27     OSAL_IRQ_PROLOGUE();
  28
  29     /* Software PWM
  30     * timer:1111 1111 1111 1111
  31     *       \_____/\/ \_______/____  count(0-255)
  32     *          \    \______________  duration of step(4)
  33     *           \__________________  index of step table(0-63)
  34     */
  35
  36     // this works for cca 65536 irqs/sec
  37     static union {
  38     uint16_t row;
  39     struct {
  40       uint8_t count:8;
  41       uint8_t duration:2;
  42       uint8_t index:6;
  43     } pwm;
  44     } timer = { .row = 0 };
  45
  46     timer.row++;
  47
  48     // LED on
  49     if (timer.pwm.count == 0) {
  50         led_set(1<<USB_LED_CAPS_LOCK);
  51     }
  52     // LED off
  53     if (timer.pwm.count == breathing_table[timer.pwm.index]) {
  54         led_set(0);
  55     }
  56
  57     /* Reset the counter */
  58     LPTMR0->CSR |= LPTMRx_CSR_TCF;
  59
  60     OSAL_IRQ_EPILOGUE();
  61 }
  62
  63 /* LPTMR clock options */
  64 #define LPTMR_CLOCK_MCGIRCLK 0 /* 4MHz clock */
  65 #define LPTMR_CLOCK_LPO      1 /* 1kHz clock */
  66 #define LPTMR_CLOCK_ERCLK32K 2 /* external 32kHz crystal */
  67 #define LPTMR_CLOCK_OSCERCLK 3 /* output from OSC */
  68
  69 /* Work around inconsistencies in Freescale naming */
  70 #if !defined(SIM_SCGC5_LPTMR)
  71 #define SIM_SCGC5_LPTMR SIM_SCGC5_LPTIMER
  72 #endif
  73
  74 /* Initialise the timer */
  75 void sleep_led_init(void) {
  76     /* Make sure the clock to the LPTMR is enabled */
  77     SIM->SCGC5 |= SIM_SCGC5_LPTMR;
  78     /* Reset LPTMR settings */
  79     LPTMR0->CSR = 0;
  80     /* Set the compare value */
  81     LPTMR0->CMR = 0;  // trigger on counter value (i.e. every time)
  82
  83     /* Set up clock source and prescaler */
  84     /* Software PWM
  85     *  ______           ______           __
  86     * |  ON  |___OFF___|  ON  |___OFF___|   ....
  87     * |<-------------->|<-------------->|<- ....
  88     *     PWM period       PWM period
  89     *
  90     * R                interrupts/period[resolution]
  91     * F                periods/second[frequency]
  92     * R * F            interrupts/second
  93     */
  94
  95     /* === OPTION 1 === */
  96     #if 0
  97     //  1kHz LPO
  98     //  No prescaler => 1024 irqs/sec
  99     //  Note: this is too slow for a smooth breathe
 100     LPTMR0->PSR = LPTMRx_PSR_PCS(LPTMR_CLOCK_LPO)|LPTMRx_PSR_PBYP;
 101     #endif /* OPTION 1 */
 102
 103     /* === OPTION 2 === */
 104     #if 1
 105     //  nMHz IRC (n=4 on KL25Z, KL26Z and K20x; n=2 or 8 on KL27Z)
 106     MCG->C2 |= MCG_C2_IRCS; // fast (4MHz) internal ref clock
 107     #if defined(KL27) // divide the 8MHz IRC by 2, to have the same MCGIRCLK speed as others
 108     MCG->MC |= MCG_MC_LIRC_DIV2_DIV2;
 109     #endif /* KL27 */
 110     MCG->C1 |= MCG_C1_IRCLKEN; // enable internal ref clock
 111     //  to work in stop mode, also MCG_C1_IREFSTEN
 112     //  Divide 4MHz by 2^N (N=6) => 62500 irqs/sec =>
 113     //  => approx F=61, R=256, duration = 4
 114     LPTMR0->PSR = LPTMRx_PSR_PCS(LPTMR_CLOCK_MCGIRCLK)|LPTMRx_PSR_PRESCALE(6);
 115     #endif /* OPTION 2 */
 116
 117     /* === OPTION 3 === */
 118     #if 0
 119     //  OSC output (external crystal), usually 8MHz or 16MHz
 120     OSC0->CR |= OSC_CR_ERCLKEN; // enable ext ref clock
 121     //  to work in stop mode, also OSC_CR_EREFSTEN
 122     //  Divide by 2^N
 123     LPTMR0->PSR = LPTMRx_PSR_PCS(LPTMR_CLOCK_OSCERCLK)|LPTMRx_PSR_PRESCALE(7);
 124     #endif /* OPTION 3 */
 125     /* === END OPTIONS === */
 126
 127     /* Interrupt on TCF set (compare flag) */
 128     nvicEnableVector(LPTMR0_IRQn, 2); // vector, priority
 129     LPTMR0->CSR |= LPTMRx_CSR_TIE;
 130 }
 131
 132 void sleep_led_enable(void) {
 133     /* Enable the timer */
 134     LPTMR0->CSR |= LPTMRx_CSR_TEN;
 135 }
 136
 137 void sleep_led_disable(void) {
 138     /* Disable the timer */
 139     LPTMR0->CSR &= ~LPTMRx_CSR_TEN;
 140 }
 141
 142 void sleep_led_toggle(void) {
 143     /* Toggle the timer */
 144     LPTMR0->CSR ^= LPTMRx_CSR_TEN;
 145 }
 146
 147 #else /* platform selection: not on familiar Kinetis chips */
 148
 149 void sleep_led_init(void) {
 150 }
 151
 152 void sleep_led_enable(void) {
 153     led_set(1<<USB_LED_CAPS_LOCK);
 154 }
 155
 156 void sleep_led_disable(void) {
 157     led_set(0);
 158 }
 159
 160 void sleep_led_toggle(void) {
 161     // not implemented
 162 }
 163
 164 #endif /* platform selection */