133 lines
4.2 KiB
C
133 lines
4.2 KiB
C
/** @addtogroup scif
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*
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* @brief <b>Access functions for the SAM4 System Controf Interface (SCIF)</b>
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* @ingroup SAM4
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* LGPL License Terms @ref lgpl_license
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* @author @htmlonly © @endhtmlonly 2016
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* Maxim Sloyko <maxims@google.com>
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*
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*/
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/*
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* This file is part of the libopencm3 project.
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*
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* This library is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this library. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <libopencm3/sam/scif.h>
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/** @brief Enable external oscillator.
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*
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* @param[in] mode enum osc_mode: Oscillator mode (which pins oscillator connected to).
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* @param[in] freq uint32_t: External Oscillator frequency, in Hertz. Must be 0.6MHz - 30MHz
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* @param[in] startup enum osc_startup: Oscillator start time in RCSYS clock cycles.
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*
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* @returns zero upon success.
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*/
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int scif_osc_enable(enum osc_mode mode, uint32_t freq, enum osc_startup startup)
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{
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uint8_t gain;
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const uint32_t kHz = 1000;
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const uint32_t MHz = 1000 * kHz;
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if (freq > 600 * kHz && freq <= 2 * MHz) {
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gain = 0;
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} else if (freq > 2 * MHz && freq <= 4 * MHz) {
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gain = 1;
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} else if (freq > 4 * MHz && freq <= 8 * MHz) {
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gain = 2;
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} else if (freq > 8 * MHz && freq <= 16 * MHz) {
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gain = 3;
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} else if (freq > 16 * MHz && freq <= 30 * MHz) {
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gain = 4;
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} else {
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return -1;
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}
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SCIF_UNLOCK = SCIF_OSCCTRL0_KEY;
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SCIF_OSCCTRL0 = mode | SCIF_OSCCTRL_OSCEN |
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(gain << SCIF_OSCCTRL_GAIN_SHIFT) | (startup << SCIF_OSCCTRL_STARTUP_SHIFT);
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while (!(SCIF_PCLKSR & SCIF_OSC0RDY));
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return 0;
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}
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/** @brief Configure and enable PLL clock.
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*
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* @param[in] delay uint8_t: Specifies the number of RCSYS clock cycles before
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* ISR.PLLLOCKn will be set after PLL has been written, or after PLL has
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* been automatically re-enabled after exiting a sleep mode.
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* @param[in] mul uint8_t: Multiply factor.
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* @param[in] div uint8_t: Division factor.These fields determine the ratio of
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* the PLL output frequency to the source oscillator frequency:
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* f_vco = (PLLMUL+1)/PLLDIV * f_ref if PLLDIV >0
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* f_vco = 2*(PLLMUL+1) * f_ref if PLLDIV = 0
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* Note that the PLLMUL field should always be greater than 1 or the
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* behavior of the PLL will be undefined.
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* @param[in] pll_opt uint8_t: PLL Options.
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*
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* @returns zero upon success.
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*/
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int scif_enable_pll(uint8_t delay, uint8_t mul, uint8_t div, uint8_t pll_opt, enum pll_clk_src source_clock)
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{
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// First, PLL needs to be disabled, otherwise the configuration register
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// is unaccessible.
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uint32_t pll_val = SCIF_PLL0;
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if (pll_val & SCIF_PLL0_PLLEN) {
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SCIF_UNLOCK = SCIF_PLL0_KEY;
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SCIF_PLL0 = pll_val & (~SCIF_PLL0_PLLEN);
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}
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if (mul == 0)
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mul = 1;
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pll_val = SCIF_PLL0_PLLOSC_MASKED(source_clock)
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| SCIF_PLL0_PLLOPT_MASKED(pll_opt)
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| SCIF_PLL0_PLLDIV_MASKED(div)
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| SCIF_PLL0_PLLMUL_MASKED(mul)
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| SCIF_PLL0_PLLCOUNT_MASKED(delay);
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SCIF_UNLOCK = SCIF_PLL0_KEY;
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SCIF_PLL0 = pll_val;
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// Now enable TODO: does this really need to be separate operation?
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SCIF_UNLOCK = SCIF_PLL0_KEY;
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SCIF_PLL0 = pll_val | SCIF_PLL0_PLLEN;
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while(!(SCIF_PCLKSR & SCIF_PLL0LOCK));
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return 0;
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}
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/** @brief Configure and enable Generic Clock
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*
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* @param[in] gclk enum generic_clock: Generic Clock to configure and enable.
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* @param[in] source_clock enum gclk_src: Source Clock for this Generic Clock.
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* @param[in] div uint16_t: Division Factor. Upper 8 bits only used for Generic Clock 11,
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* If 0, clock is undivided.
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*/
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void scif_enable_gclk(enum generic_clock gclk, enum gclk_src source_clock, uint16_t div)
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{
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uint32_t reg_val = SCIF_GCCTRL_CEN | SCIF_GCCTRL_OSCSEL_MASKED(source_clock);
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if (div) {
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if (gclk < GENERIC_CLOCK11) {
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div &= 0xf;
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}
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reg_val |= SCIF_GCCTRL_DIV_MASKED(div) | SCIF_GCCTRL_DIVEN;
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}
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SCIF_GCTRL(gclk) = reg_val;
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}
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