altos/cc1111: Wait for xtal to be stable

[fw/altos] / src / cc1111 / ao_timer.c

diff --git a/src/cc1111/ao_timer.c b/src/cc1111/ao_timer.c
index 54af9605b59bb997fa75b89508bb45e41f06e8d8..d681f51bb6689e224bbf2aa259f230a4fd182801 100644 (file)
--- a/src/cc1111/ao_timer.c
+++ b/src/cc1111/ao_timer.c
@@ -83,18 +83,48 @@ ao_timer_init(void)
        T1CTL = T1CTL_MODE_MODULO | T1CTL_DIV_8;
 }
 
+static void
+ao_clock_delay(void)
+{
+       uint16_t        i = 0;
+
+       while (--i)
+               ao_arch_nop();
+}
+
 /*
  * AltOS always cranks the clock to the max frequency
  */
 void
 ao_clock_init(void)
 {
+       /* Power up both oscillators */
+       SLEEP &= ~(SLEEP_OSC_PD);
+
+       /* Switch to the HFRC oscillator */
+       CLKCON = (CLKCON & ~CLKCON_OSC_MASK) | (CLKCON_OSC_RC);
+
+       /* Wait for the HFRC oscillator to be stable */
+       while (!(SLEEP & SLEEP_HFRC_STB))
+               ;
+
+       /* Delay for 'a while' waiting for the crystal to
+        * stabilize -- the XOSC_STB bit isn't reliable
+        *
+        *  http://www.ti.com/lit/er/swrz022c/swrz022c.pdf
+        */
+
+       ao_clock_delay();
+
        /* Switch system clock to crystal oscilator */
        CLKCON = (CLKCON & ~CLKCON_OSC_MASK) | (CLKCON_OSC_XTAL);
 
-       while (!(SLEEP & SLEEP_XOSC_STB))
-               ;
+       /* Power down the unused HFRC oscillator */
+       SLEEP |= SLEEP_OSC_PD;
 
+       /* Wait for HFRC to power down */
+       while ((SLEEP & SLEEP_HFRC_STB) != 0)
+               ;
        /* Crank up the timer tick and system clock speed */
        CLKCON = ((CLKCON & ~(CLKCON_TICKSPD_MASK | CLKCON_CLKSPD_MASK)) |
                  (CLKCON_TICKSPD_1 | CLKCON_CLKSPD_1));