Diff: mbed-dev/targets/TARGET_NXP/TARGET_LPC15XX/us_ticker.c

Revision:

18:6a4db94011d3

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-dev/targets/TARGET_NXP/TARGET_LPC15XX/us_ticker.c	Sun May 14 23:18:57 2017 +0000
@@ -0,0 +1,83 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2006-2013 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include <stddef.h>
+#include "us_ticker_api.h"
+#include "PeripheralNames.h"
+#include "mbed_critical.h"
+
+#define US_TICKER_TIMER_IRQn     SCT3_IRQn
+
+int us_ticker_inited = 0;
+
+void us_ticker_init(void) {
+    if (us_ticker_inited)
+        return;
+
+    us_ticker_inited = 1;
+
+    // Enable the SCT3 clock
+    LPC_SYSCON->SYSAHBCLKCTRL1 |= (1 << 5);
+
+    // Clear peripheral reset the SCT3
+    LPC_SYSCON->PRESETCTRL1 |= (1 << 5);
+    LPC_SYSCON->PRESETCTRL1 &= ~(1 << 5);
+
+    // Configure SCT3 as a 1MHz 32-bit counter with no auto limiting or match reload
+    char sctClkDiv = ((SystemCoreClock + 1000000 - 1) / 1000000) - 1;
+    LPC_SCT3->CONFIG = (1 << 7) | (1 << 0);
+    LPC_SCT3->CTRL = (sctClkDiv << 5) | (1 << 3) | (1 << 2);
+
+    // Configure SCT3 event 0 to fire on match register 0
+    LPC_SCT3->EV0_STATE = (1 << 0);
+    LPC_SCT3->EV0_CTRL = (0x1 << 12);
+
+    // Start SCT3
+    LPC_SCT3->CTRL &= ~(1 << 2);
+
+    // Set SCT3 interrupt vector
+    NVIC_SetVector(US_TICKER_TIMER_IRQn, (uint32_t)us_ticker_irq_handler);
+    NVIC_EnableIRQ(US_TICKER_TIMER_IRQn);
+}
+
+uint32_t us_ticker_read() {
+    if (!us_ticker_inited)
+        us_ticker_init();
+
+    // Return SCT3 count value
+    return LPC_SCT3->COUNT;
+}
+
+void us_ticker_set_interrupt(timestamp_t timestamp) {
+    // Set SCT3 match register 0 (critical section)
+    core_util_critical_section_enter();
+    LPC_SCT3->CTRL |= (1 << 2);
+    LPC_SCT3->MATCH0 = (uint32_t)timestamp;
+    LPC_SCT3->CTRL &= ~(1 << 2);
+    core_util_critical_section_exit();
+
+    // Enable interrupt on SCT3 event 0
+    LPC_SCT3->EVEN = (1 << 0);
+}
+
+void us_ticker_disable_interrupt(void) {
+    // Disable interrupt on SCT3 event 0
+    LPC_SCT3->EVEN = 0;
+}
+
+void us_ticker_clear_interrupt(void) {
+    // Clear SCT3 event 0 interrupt flag
+    LPC_SCT3->EVFLAG = (1 << 0);
+}