X-Git-Url: https://codewiz.org/gitweb?a=blobdiff_plain;f=bertos%2Fdrv%2Fntc.c;fp=bertos%2Fdrv%2Fntc.c;h=2469c88f00ac61514814a8ecdf250d32fa463733;hb=791e167e053bdd9250d34a9a5ccae6ccde4d6679;hp=0000000000000000000000000000000000000000;hpb=faf2f6bfd5933ff75e6cc01e3d48f9277f731d8f;p=bertos.git

diff --git a/bertos/drv/ntc.c b/bertos/drv/ntc.c
new file mode 100644
index 00000000..2469c88f
--- /dev/null
+++ b/bertos/drv/ntc.c
@@ -0,0 +1,161 @@
+/**
+ * \file
+ * <!--
+ * This file is part of BeRTOS.
+ *
+ * Bertos is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ * As a special exception, you may use this file as part of a free software
+ * library without restriction.  Specifically, if other files instantiate
+ * templates or use macros or inline functions from this file, or you compile
+ * this file and link it with other files to produce an executable, this
+ * file does not by itself cause the resulting executable to be covered by
+ * the GNU General Public License.  This exception does not however
+ * invalidate any other reasons why the executable file might be covered by
+ * the GNU General Public License.
+ *
+ * Copyright 2004, 2005 Develer S.r.l. (http://www.de+veler.com/)
+ * All Rights Reserved.
+ * -->
+ *
+ * \brief Driver for NTC (reads a temperature through an ADC)
+ *
+ * \version $Id$
+ *
+ * \author Giovanni Bajo <rasky@develer.com>
+ * \author Francesco Sacchi <batt@develer.com>
+ *
+ *
+ * This module handles an external NTC bound to an AD converter. As usual,
+ * it relies on a low-level API (ntc_hw_*) (see below):
+ *
+ */
+
+/*#*
+ *#* $Log$
+ *#* Revision 1.2  2006/07/19 12:56:26  bernie
+ *#* Convert to new Doxygen style.
+ *#*
+ *#* Revision 1.1  2005/11/04 17:59:47  bernie
+ *#* Import into DevLib.
+ *#*
+ *#* Revision 1.1  2005/05/24 09:17:58  batt
+ *#* Move drivers to top-level.
+ *#*/
+
+#include <drv/ntc.h>
+#include <hw_ntc.h>
+#include <ntc_map.h>
+
+#include <cfg/debug.h>
+
+DB(bool ntc_initialized;)
+
+/**
+ * Find in a table of values \a orig_table of size \a size, the index which
+ * value is less or equal to \a val.
+ *
+ * \retval 0 When \a val is higher than the first table entry.
+ * \retval size When \a val is lower than the last table entry.
+ * \retval 1..size-1 When \a val is within the table.
+ */
+static size_t upper_bound(const res_t *orig_table, size_t size, res_t val)
+{
+	const res_t *table = orig_table;
+
+	while (size)
+	{
+		size_t pos = size / 2;
+		if (val > table[pos])
+			size = pos;
+		else
+		{
+			table += pos+1;
+			size -= pos+1;
+		}
+	}
+
+	return table - orig_table;
+}
+
+
+/**
+ * Read the temperature for the NTC channel \a dev.
+ * First read the resistence of the NTC through ntc_hw_read(), then,
+ * for the conversion from resistance to temperature, since the formula
+ * varies from device to device, we implemented a generic system using
+ * a table of data which maps temperature (index) to resistance (data).
+ * The range of the table (min/max temperature) and the step
+ * (temperature difference between two consecutive elements of the table)
+ * is variable and can be specified. Notice that values inbetween the
+ * table elements are still possible as the library does a linear
+ * interpolation using the actual calculated resistance to find out
+ * the exact temperature.
+ *
+ * The low-level API provides a function to get access to a description
+ * of the NTC (ntc_hw_getInfo()), including the resistance table.
+ *
+ */
+deg_t ntc_read(NtcDev dev)
+{
+	const NtcHwInfo* hw = ntc_hw_getInfo(dev);
+	const res_t* r = hw->resistances;
+
+	float rx;
+	size_t i;
+	deg_t degrees;
+
+	rx = ntc_hw_read(dev);
+
+
+	i = upper_bound(r, hw->num_resistances, rx);
+	ASSERT(i <= hw->num_resistances);
+
+	if (i >= hw->num_resistances)
+		return NTC_SHORT_CIRCUIT;
+	else if (i == 0)
+		return NTC_OPEN_CIRCUIT;
+
+	/*
+	 * Interpolated value in 0.1 degrees multiplied by 10:
+	 *   delta t          step t
+	 * ----------  = ----------------
+	 * (rx - r[i])   (r[i-1] - r [i])
+	 */
+	float tmp;
+	tmp = 10 * hw->degrees_step * (rx - r[i]) / (r[i - 1] - r[i]);
+
+	/*
+	 * degrees = integer part corresponding to the superior index
+	 *           in the table multiplied by 10
+	 *           - decimal part interpolated (already multiplied by 10)
+	 */
+	degrees = (i * hw->degrees_step + hw->degrees_min) * 10 - (int)(tmp);
+
+	//kprintf("dev= %d, I=%d, degrees = %d\n", dev, i , degrees);
+
+	return degrees;
+}
+
+
+/**
+ * Init NTC hardware.
+ */
+void ntc_init(void)
+{
+	NTC_HW_INIT;
+	DB(ntc_initialized = true;)
+}
+