Initial Release

src/rp2_common/hardware_pll/CMakeLists.txt

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+pico_simple_hardware_target(pll)

src/rp2_common/hardware_pll/include/hardware/pll.h

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+/*
+ * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef _HARDWARE_PLL_H_
+#define _HARDWARE_PLL_H_
+
+#include "pico.h"
+#include "hardware/structs/pll.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** \file hardware/pll.h
+ *  \defgroup hardware_pll hardware_pll
+ *
+ * Phase Locked Loop control APIs
+ *
+ * There are two PLLs in RP2040. They are:
+ *   - pll_sys - Used to generate up to a 133MHz system clock
+ *   - pll_usb - Used to generate a 48MHz USB reference clock
+ *
+ * For details on how the PLL's are calculated, please refer to the RP2040 datasheet.
+ */
+
+typedef pll_hw_t *PLL;
+
+#define pll_sys pll_sys_hw
+#define pll_usb pll_usb_hw
+
+/*! \brief Initialise specified PLL.
+ *  \ingroup hardware_pll
+ * \param pll pll_sys or pll_usb
+ * \param ref_div Input clock divider.
+ * \param vco_freq  Requested output from the VCO (voltage controlled oscillator)
+ * \param post_div1 Post Divider 1 - range 1-7. Must be >= post_div2
+ * \param post_div2 Post Divider 2 - range 1-7
+ */
+void pll_init(PLL pll, uint32_t ref_div, uint32_t vco_freq, uint32_t post_div1, uint8_t post_div2);
+
+/*! \brief Release/uninitialise specified PLL.
+ *  \ingroup hardware_pll
+ *
+ * This will turn off the power to the specified PLL. Note this function does not currently check if
+ * the PLL is in use before powering it off so should be used with care.
+ *
+ * \param pll pll_sys or pll_usb
+ */
+void pll_deinit(PLL pll);
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif

src/rp2_common/hardware_pll/pll.c

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+/*
+ * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+// For MHZ definitions etc
+#include "hardware/clocks.h"
+#include "hardware/pll.h"
+
+/// \tag::pll_init_calculations[]
+void pll_init(PLL pll, uint32_t refdiv, uint32_t vco_freq, uint32_t post_div1, uint8_t post_div2) {
+    // Turn off PLL in case it is already running
+    pll->pwr = 0xffffffff;
+    pll->fbdiv_int = 0;
+
+    uint32_t ref_mhz = XOSC_MHZ / refdiv;
+    pll->cs = refdiv;
+
+    // What are we multiplying the reference clock by to get the vco freq
+    // (The regs are called div, because you divide the vco output and compare it to the refclk)
+    uint32_t fbdiv = vco_freq / (ref_mhz * MHZ);
+/// \end::pll_init_calculations[]
+
+    // fbdiv
+    assert(fbdiv >= 16 && fbdiv <= 320);
+
+    // Check divider ranges
+    assert((post_div1 >= 1 && post_div1 <= 7) && (post_div2 >= 1 && post_div2 <= 7));
+
+    // post_div1 should be >= post_div2
+    // from appnote page 11
+    // postdiv1 is designed to operate with a higher input frequency
+    // than postdiv2
+    assert(post_div2 <= post_div1);
+
+/// \tag::pll_init_finish[]
+    // Check that reference frequency is no greater than vco / 16
+    assert(ref_mhz <= (vco_freq / 16));
+
+    // Put calculated value into feedback divider
+    pll->fbdiv_int = fbdiv;
+
+    // Turn on PLL
+    uint32_t power = PLL_PWR_PD_BITS | // Main power
+                     PLL_PWR_VCOPD_BITS; // VCO Power
+
+    hw_clear_bits(&pll->pwr, power);
+
+    // Wait for PLL to lock
+    while (!(pll->cs & PLL_CS_LOCK_BITS)) tight_loop_contents();
+
+    // Set up post dividers - div1 feeds into div2 so if div1 is 5 and div2 is 2 then you get a divide by 10
+    uint32_t pdiv = (post_div1 << PLL_PRIM_POSTDIV1_LSB) |
+                    (post_div2 << PLL_PRIM_POSTDIV2_LSB);
+    pll->prim = pdiv;
+
+    // Turn on post divider
+    hw_clear_bits(&pll->pwr, PLL_PWR_POSTDIVPD_BITS);
+/// \end::pll_init_finish[]
+}
+
+void pll_deinit(PLL pll) {
+    // todo: Make sure there are no sources running from this pll?
+    pll->pwr = PLL_PWR_BITS;
+}