linux boards (ocpoc, bbblue, navio2) replace custom adc drivers with simple px4_arch implementation

boards/emlid/navio2/adc/adc.cpp

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+/****************************************************************************
+ *
+ *   Copyright (C) 2020 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+#include <board_config.h>
+
+#include <drivers/drv_adc.h>
+
+#include <px4_platform_common/log.h>
+
+#include <fcntl.h>
+#include <stdint.h>
+#include <unistd.h>
+
+#define ADC_SYSFS_PATH "/sys/kernel/rcio/adc"
+#define ADC_MAX_CHAN 6
+int _channels_fd[ADC_MAX_CHAN];
+
+int px4_arch_adc_init(uint32_t base_address)
+{
+	for (int i = 0; i < ADC_MAX_CHAN; i++) {
+		_channels_fd[i] = -1;
+	}
+
+	return 0;
+}
+
+void px4_arch_adc_uninit(uint32_t base_address)
+{
+	for (int i = 0; i < ADC_MAX_CHAN; i++) {
+		::close(_channels_fd[i]);
+		_channels_fd[i] = -1;
+	}
+}
+
+uint32_t px4_arch_adc_sample(uint32_t base_address, unsigned channel)
+{
+	if (channel > ADC_MAX_CHAN) {
+		PX4_ERR("channel %d out of range: %d", channel, ADC_MAX_CHAN);
+		return UINT32_MAX; // error
+	}
+
+	// open channel if necessary
+	if (_channels_fd[channel] == -1) {
+		// ADC_SYSFS_PATH
+		char channel_path[strlen(ADC_SYSFS_PATH) + 5] {};
+
+		if (sprintf(channel_path, "%s/ch%d", ADC_SYSFS_PATH, channel) == -1) {
+			PX4_ERR("adc channel: %d\n", channel);
+			return UINT32_MAX; // error
+		}
+
+		_channels_fd[channel] = ::open(channel_path, O_RDONLY);
+	}
+
+	char buffer[10] {};
+
+	if (::pread(_channels_fd[channel], buffer, sizeof(buffer), 0) < 0) {
+		PX4_ERR("read channel %d failed", channel);
+		return UINT32_MAX; // error
+	}
+
+	return atoi(buffer);
+}
+
+uint32_t px4_arch_adc_dn_fullcount()
+{
+	return 1 << 12; // 12 bit ADC
+}