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app_util.h

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00001 /* Copyright (c) 2012 Nordic Semiconductor. All Rights Reserved.
00002  *
00003  * The information contained herein is property of Nordic Semiconductor ASA.
00004  * Terms and conditions of usage are described in detail in NORDIC
00005  * SEMICONDUCTOR STANDARD SOFTWARE LICENSE AGREEMENT.
00006  *
00007  * Licensees are granted free, non-transferable use of the information. NO
00008  * WARRANTY of ANY KIND is provided. This heading must NOT be removed from
00009  * the file.
00010  *
00011  */
00012 
00013 /** @file
00014  *
00015  * @defgroup app_util Utility Functions and Definitions
00016  * @{
00017  * @ingroup app_common
00018  *
00019  * @brief Various types and definitions available to all applications.
00020  */
00021 
00022 #ifndef APP_UTIL_H__
00023 #define APP_UTIL_H__
00024 
00025 #include <stdint.h>
00026 #include <stdbool.h>
00027 #include "compiler_abstraction.h"
00028 
00029 enum
00030 {
00031     UNIT_0_625_MS = 625,                                /**< Number of microseconds in 0.625 milliseconds. */
00032     UNIT_1_25_MS  = 1250,                               /**< Number of microseconds in 1.25 milliseconds. */
00033     UNIT_10_MS    = 10000                               /**< Number of microseconds in 10 milliseconds. */
00034 };
00035 
00036 /**@brief Macro for doing static (i.e. compile time) assertion.
00037  *
00038  * @note If the assertion fails when compiling using Keil, the compiler will report error message
00039  *       "error: #94: the size of an array must be greater than zero" (while gcc will list the
00040  *       symbol static_assert_failed, making the error message more readable).
00041  *       If the supplied expression can not be evaluated at compile time, Keil will report
00042  *       "error: #28: expression must have a constant value".
00043  *
00044  * @note The macro is intentionally implemented not using do while(0), allowing it to be used
00045  *       outside function blocks (e.g. close to global type- and variable declarations).
00046  *       If used in a code block, it must be used before any executable code in this block.
00047  *
00048  * @param[in]   EXPR   Constant expression to be verified.
00049  */
00050 
00051 #if defined(__GNUC__)
00052 #define STATIC_ASSERT(EXPR) typedef char __attribute__((unused)) static_assert_failed[(EXPR) ? 1 : -1]
00053 #else
00054 #define STATIC_ASSERT(EXPR) typedef char static_assert_failed[(EXPR) ? 1 : -1]
00055 #endif
00056 
00057 
00058 /**@brief type for holding an encoded (i.e. little endian) 16 bit unsigned integer. */
00059 typedef uint8_t uint16_le_t[2];
00060 
00061 /**@brief type for holding an encoded (i.e. little endian) 32 bit unsigned integer. */
00062 typedef uint8_t uint32_le_t[4];
00063 
00064 /**@brief Byte array type. */
00065 typedef struct
00066 {
00067     uint16_t  size;                 /**< Number of array entries. */
00068     uint8_t * p_data;               /**< Pointer to array entries. */
00069 } uint8_array_t;
00070     
00071 /**@brief Perform rounded integer division (as opposed to truncating the result).
00072  *
00073  * @param[in]   A   Numerator.
00074  * @param[in]   B   Denominator.
00075  *
00076  * @return      Rounded (integer) result of dividing A by B.
00077  */
00078 #define ROUNDED_DIV(A, B) (((A) + ((B) / 2)) / (B))
00079 
00080 /**@brief Check if the integer provided is a power of two.
00081  *
00082  * @param[in]   A   Number to be tested.
00083  *
00084  * @return      true if value is power of two.
00085  * @return      false if value not power of two.
00086  */
00087 #define IS_POWER_OF_TWO(A) ( ((A) != 0) && ((((A) - 1) & (A)) == 0) )
00088 
00089 /**@brief To convert milliseconds to ticks.
00090  * @param[in] TIME          Number of milliseconds to convert.
00091  * @param[in] RESOLUTION    Unit to be converted to in [us/ticks].
00092  */
00093 #define MSEC_TO_UNITS(TIME, RESOLUTION) (((TIME) * 1000) / (RESOLUTION))
00094 
00095 
00096 /**@brief Perform integer division, making sure the result is rounded up.
00097  *
00098  * @details One typical use for this is to compute the number of objects with size B is needed to
00099  *          hold A number of bytes.
00100  *
00101  * @param[in]   A   Numerator.
00102  * @param[in]   B   Denominator.
00103  *
00104  * @return      Integer result of dividing A by B, rounded up.
00105  */
00106 #define CEIL_DIV(A, B)      \
00107     /*lint -save -e573 */   \
00108     ((((A) - 1) / (B)) + 1) \
00109     /*lint -restore */
00110 
00111 /**@brief Function for encoding a uint16 value.
00112  *
00113  * @param[in]   value            Value to be encoded.
00114  * @param[out]  p_encoded_data   Buffer where the encoded data is to be written.
00115  *
00116  * @return      Number of bytes written.
00117  */
00118 static __INLINE uint8_t uint16_encode(uint16_t value, uint8_t * p_encoded_data)
00119 {
00120     p_encoded_data[0] = (uint8_t) ((value & 0x00FF) >> 0);
00121     p_encoded_data[1] = (uint8_t) ((value & 0xFF00) >> 8);
00122     return sizeof(uint16_t);
00123 }
00124     
00125 /**@brief Function for encoding a uint32 value.
00126  *
00127  * @param[in]   value            Value to be encoded.
00128  * @param[out]  p_encoded_data   Buffer where the encoded data is to be written.
00129  *
00130  * @return      Number of bytes written.
00131  */
00132 static __INLINE uint8_t uint32_encode(uint32_t value, uint8_t * p_encoded_data)
00133 {
00134     p_encoded_data[0] = (uint8_t) ((value & 0x000000FF) >> 0);
00135     p_encoded_data[1] = (uint8_t) ((value & 0x0000FF00) >> 8);
00136     p_encoded_data[2] = (uint8_t) ((value & 0x00FF0000) >> 16);
00137     p_encoded_data[3] = (uint8_t) ((value & 0xFF000000) >> 24);
00138     return sizeof(uint32_t);
00139 }
00140 
00141 /**@brief Function for decoding a uint16 value.
00142  *
00143  * @param[in]   p_encoded_data   Buffer where the encoded data is stored.
00144  *
00145  * @return      Decoded value.
00146  */
00147 static __INLINE uint16_t uint16_decode(const uint8_t * p_encoded_data)
00148 {
00149         return ( (((uint16_t)((uint8_t *)p_encoded_data)[0])) | 
00150                  (((uint16_t)((uint8_t *)p_encoded_data)[1]) << 8 ));
00151 }
00152 
00153 /**@brief Function for decoding a uint32 value.
00154  *
00155  * @param[in]   p_encoded_data   Buffer where the encoded data is stored.
00156  *
00157  * @return      Decoded value.
00158  */
00159 static __INLINE uint32_t uint32_decode(const uint8_t * p_encoded_data)
00160 {
00161     return ( (((uint32_t)((uint8_t *)p_encoded_data)[0]) << 0)  |
00162              (((uint32_t)((uint8_t *)p_encoded_data)[1]) << 8)  |
00163              (((uint32_t)((uint8_t *)p_encoded_data)[2]) << 16) |
00164              (((uint32_t)((uint8_t *)p_encoded_data)[3]) << 24 ));
00165 }
00166     
00167 /** @brief Function for converting the input voltage (in milli volts) into percentage of 3.0 Volts.
00168  *
00169  *  @details The calculation is based on a linearized version of the battery's discharge
00170  *           curve. 3.0V returns 100% battery level. The limit for power failure is 2.1V and
00171  *           is considered to be the lower boundary.
00172  *
00173  *           The discharge curve for CR2032 is non-linear. In this model it is split into
00174  *           4 linear sections:
00175  *           - Section 1: 3.0V - 2.9V = 100% - 42% (58% drop on 100 mV)
00176  *           - Section 2: 2.9V - 2.74V = 42% - 18% (24% drop on 160 mV)
00177  *           - Section 3: 2.74V - 2.44V = 18% - 6% (12% drop on 300 mV)
00178  *           - Section 4: 2.44V - 2.1V = 6% - 0% (6% drop on 340 mV)
00179  *
00180  *           These numbers are by no means accurate. Temperature and
00181  *           load in the actual application is not accounted for!
00182  *
00183  *  @param[in] mvolts The voltage in mV
00184  *
00185  *  @return    Battery level in percent.
00186 */
00187 static __INLINE uint8_t battery_level_in_percent(const uint16_t mvolts)
00188 {
00189     uint8_t battery_level;
00190 
00191     if (mvolts >= 3000)
00192     {
00193         battery_level = 100;
00194     }
00195     else if (mvolts > 2900)
00196     {
00197         battery_level = 100 - ((3000 - mvolts) * 58) / 100;
00198     }
00199     else if (mvolts > 2740)
00200     {
00201         battery_level = 42 - ((2900 - mvolts) * 24) / 160;
00202     }
00203     else if (mvolts > 2440)
00204     {
00205         battery_level = 18 - ((2740 - mvolts) * 12) / 300;
00206     }
00207     else if (mvolts > 2100)
00208     {
00209         battery_level = 6 - ((2440 - mvolts) * 6) / 340;
00210     }
00211     else
00212     {
00213         battery_level = 0;
00214     }
00215 
00216     return battery_level;
00217 }
00218 
00219 /**@brief Function for checking if a pointer value is aligned to a 4 byte boundary.
00220  *
00221  * @param[in]   p   Pointer value to be checked.
00222  *
00223  * @return      TRUE if pointer is aligned to a 4 byte boundary, FALSE otherwise.
00224  */
00225 static __INLINE bool is_word_aligned(void * p)
00226 {
00227     return (((uintptr_t)p & 0x03) == 0);
00228 }
00229 
00230 #endif // APP_UTIL_H__
00231 
00232 /** @} */