tests: gadget0: efm32hg: add gadget0 test for efm32hg

tests/gadget-zero/delay_efm32.c

@@ -0,0 +1,45 @@
+/*
+ * This file is part of the libopencm3 project.
+ *
+ * Copyright (C) 2018 Seb Holzapfel <schnommus@gmail.com>
+ *
+ * This library is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this library.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdint.h>
+#include <libopencm3/efm32/cmu.h>
+#include <libopencm3/efm32/timer.h>
+
+#include "delay.h"
+
+extern const uint32_t ahb_frequency;
+
+void delay_setup(void)
+{
+	cmu_periph_clock_enable(CMU_TIMER2);
+	/* efm32hg doesn't support a nice 1us prescaler */
+	timer_start(TIMER2);
+}
+
+void delay_us(uint16_t us)
+{
+	volatile uint16_t time_now = 0;
+	/* Convert microseconds into timer ticks */
+	uint16_t delay_ahb_cycles = us * (ahb_frequency / 1000000);
+
+	TIMER2_CNT = 0;
+	while (time_now < delay_ahb_cycles) {
+		time_now = TIMER2_CNT;
+	}
+}