modules/pins/analog: add adc for the esp32 #37

Author: fivdi

modules/pins/analog/esp32/analog.c

@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2016-2018  Moddable Tech, Inc.
+ *
+ *   This file is part of the Moddable SDK Runtime.
+ * 
+ *   The Moddable SDK Runtime 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.
+ * 
+ *   The Moddable SDK Runtime 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 the Moddable SDK Runtime.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "xs.h"
+#include "xsesp.h"
+
+#include "driver/adc.h"
+#include "esp_adc_cal/include/esp_adc_cal.h"
+
+#define V_REF 1100
+
+void xs_analog_read(xsMachine *the)
+{
+	int channel = xsToInteger(xsArg(0));
+	if (channel < 0 || channel >= ADC1_CHANNEL_MAX)
+		xsRangeError("invalid analog channel number");
+
+	if (ESP_OK != adc1_config_width(ADC_WIDTH_BIT_10))
+		xsUnknownError("can't configure precision for ADC1 peripheral");
+
+	if (ESP_OK != adc1_config_channel_atten(channel, ADC_ATTEN_DB_11))
+		xsUnknownError("can't configure attenuation for requested channel on ADC1 peripheral");
+
+	esp_adc_cal_characteristics_t characteristics;
+	esp_adc_cal_get_characteristics(V_REF, ADC_ATTEN_DB_11, ADC_WIDTH_BIT_10, &characteristics);
+
+	uint32_t milli_volts = adc1_to_voltage(channel, &characteristics);
+	uint32_t linear_raw_value = c_round(milli_volts / 3300.0 * 1023.0);
+
+	xsResult = xsInteger(linear_raw_value);
+}
+