knx/datapoint_types.cpp

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2018-04-09 22:30:23 +02:00
/*
* datapoint_types.h - Conversion functions for datapoint types.
*
* Copyright (c) 2014 Stefan Taferner <stefan.taferner@gmx.at>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*/
#include "datapoint_types.h"
#include <stdint.h>
// Sign for a negative DPT9 float value
#define DPT_FLOAT_NEG_SIGN 0x8000
uint16_t dptToFloat(int32_t value)
{
uint16_t exp = 0;
if (value < -67108864 || value > 67076096)
return 0x7fff;
if (value < 0)
{
while (value < -2048)
{
value >>= 1;
++exp;
}
return DPT_FLOAT_NEG_SIGN | (((int32_t) value) & 2047) | (exp << 11);
}
else
{
while (value > 2047)
{
value >>= 1;
++exp;
}
return value | (exp << 11);
}
}
int32_t dptFromFloat(uint16_t dptValue)
{
uint16_t exp = (dptValue >> 11) & 15;
int32_t value;
if (dptValue == 0x7fff)
return INVALID_DPT_FLOAT;
if (dptValue >= 0x8000)
value = dptValue | (-1L & ~2047);
else value = dptValue & 2047;
for (; exp; --exp)
value <<= 1;
return value;
}