ieee802154: add helpers for RSSI and dBm conversion

sys/include/net/ieee802154.h

@@ -422,6 +422,49 @@ static inline eui64_t *ieee802154_get_iid(eui64_t *eui64, const uint8_t *addr,
     return eui64;
 }
 
+/**
+ * @brief Convert from RSSI scale to dBm.
+ *
+ * The RSSI calculation is based on the IEEE 802.15.4 2020 specification and
+ * it's represented as one octet of integer.
+ *
+ * RSSI equal to zero maps to -174 dBm and has the same scale as dBm (1 RSSI
+ * step == 1 dBm). Therefore an RSSI value of 254 maps to +80 dBm.
+ *
+ * @note RSSI == 255 is defined as reserved by the standard and ignored by this
+ * function.
+ *
+ * @param[in] rssi RF power in RSSI scale
+ *
+ * @return RF power in dBm scale
+ */
+static inline int16_t ieee802154_rssi_to_dbm(uint8_t rssi)
+{
+    return rssi + IEEE802154_RADIO_RSSI_OFFSET;
+}
+
+/**
+ * @brief Convert from dBm scale to RSSI.
+ *
+ * The RSSI calculation is based on the IEEE 802.15.4 2020 specification and
+ * it's represented as one octet of integer.
+ *
+ * RSSI equal to zero maps to -174 dBm and has the same scale as dBm (1 RSSI
+ * step == 1 dBm). Therefore an RSSI value of 254 maps to +80 dBm.
+ *
+ * @param[in] dbm RF power in dBm scale.
+ *
+ * @return RF power in RSSI scale.
+ */
+static inline uint8_t ieee802154_dbm_to_rssi(int16_t dbm)
+{
+    const int min = IEEE802154_RADIO_RSSI_OFFSET;
+    const int max = min + (UINT8_MAX - 1);
+
+    int val = dbm <= min ? min : (dbm >= max ? max : dbm);
+    return val - IEEE802154_RADIO_RSSI_OFFSET;
+}
+
 #ifdef __cplusplus
 }
 #endif