+#if defined(KL2x) || defined(K20x) /* platform selection: familiar Kinetis chips */
+/* All right, we go the "software" way: LP timer, toggle LED in interrupt.
+ * Based on hasu's code for AVRs.
+ */
+
+/* Breathing Sleep LED brighness(PWM On period) table
+ * (64[steps] * 4[duration]) / 64[PWM periods/s] = 4 second breath cycle
+ *
+ * http://www.wolframalpha.com/input/?i=%28sin%28+x%2F64*pi%29**8+*+255%2C+x%3D0+to+63
+ * (0..63).each {|x| p ((sin(x/64.0*PI)**8)*255).to_i }
+ */
+static const uint8_t breathing_table[64] = {
+0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 4, 6, 10,
+15, 23, 32, 44, 58, 74, 93, 113, 135, 157, 179, 199, 218, 233, 245, 252,
+255, 252, 245, 233, 218, 199, 179, 157, 135, 113, 93, 74, 58, 44, 32, 23,
+15, 10, 6, 4, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+};
+
+/* Low Power Timer interrupt handler */
+OSAL_IRQ_HANDLER(KINETIS_LPTMR0_IRQ_VECTOR) {
+ OSAL_IRQ_PROLOGUE();
+
+ /* Software PWM
+ * timer:1111 1111 1111 1111
+ * \_____/\/ \_______/____ count(0-255)
+ * \ \______________ duration of step(4)
+ * \__________________ index of step table(0-63)
+ */
+
+ // this works for cca 65536 irqs/sec
+ static union {
+ uint16_t row;
+ struct {
+ uint8_t count:8;
+ uint8_t duration:2;
+ uint8_t index:6;
+ } pwm;
+ } timer = { .row = 0 };
+
+ timer.row++;
+
+ // LED on
+ if (timer.pwm.count == 0) {
+ led_set(1<<USB_LED_CAPS_LOCK);
+ }
+ // LED off
+ if (timer.pwm.count == breathing_table[timer.pwm.index]) {
+ led_set(0);
+ }
+
+ /* Reset the counter */
+ LPTMR0->CSR |= LPTMRx_CSR_TCF;
+
+ OSAL_IRQ_EPILOGUE();
+}
+
+/* LPTMR clock options */
+#define LPTMR_CLOCK_MCGIRCLK 0 /* 4MHz clock */
+#define LPTMR_CLOCK_LPO 1 /* 1kHz clock */
+#define LPTMR_CLOCK_ERCLK32K 2 /* external 32kHz crystal */
+#define LPTMR_CLOCK_OSCERCLK 3 /* output from OSC */
+
+/* Work around inconsistencies in Freescale naming */
+#if !defined(SIM_SCGC5_LPTMR)
+#define SIM_SCGC5_LPTMR SIM_SCGC5_LPTIMER
+#endif
+
+/* Initialise the timer */