add SNR, RSSI, and wideband RSSI measurement

Inc/sx127x.h

@@ -32,5 +32,8 @@ typedef struct sx127x_s {
 int32_t sx127x_init(sx127x_t *sx127x, SPI_HandleTypeDef *hspi, GPIO_TypeDef *port, uint16_t pin);
 int32_t sx127x_tx(sx127x_t *sx127x, uint8_t *buf, uint16_t len);
 int32_t sx127x_rx(sx127x_t *sx127x, uint8_t *buf);
+int32_t sx127x_snr(sx127x_t *sx127x);
+int32_t sx127x_rssi(sx127x_t *sx127x);
+int32_t sx127x_rand(sx127x_t *sx127x);
 
 #endif /* SX127X_INC_SX127X_H_ */

Src/sx127x.c

@@ -269,6 +269,9 @@ int32_t sx127x_tx(sx127x_t *sx127x, uint8_t *buf, uint16_t len)
 	uint16_t i;
 	uint8_t tmp;
 
+	return_val_if_fail(sx127x, -1);
+	return_val_if_fail(buf, -1);
+
 	/*
 	 * FIFO can be prefilled in Sleep/Standby but must be refilled “on-the-fly” during Tx with the rest of the payload.
 	 * 1) Pre-fill FIFO (in Sleep/Standby first or directly in Tx mode) until FifoThreshold or FifoFull is set
@@ -306,6 +309,9 @@ int32_t sx127x_rx(sx127x_t *sx127x, uint8_t *buf)
 	uint8_t len;
 	uint8_t ptr;
 
+	return_val_if_fail(sx127x, -1);
+	return_val_if_fail(buf, -1);
+
 	/*
 	 * In continuous mode the received packet processing sequence is given below.
 	 * 1 Whilst in Sleep or Standby mode select RXCONT mode.
@@ -375,6 +381,61 @@ int32_t sx127x_rx(sx127x_t *sx127x, uint8_t *buf)
 	return len;
 }
 
+int32_t sx127x_snr(sx127x_t *sx127x)
+{
+	uint8_t tmp;
+
+	return_val_if_fail(sx127x, INT32_MIN);
+
+	/* read SNR from register as two's complement, multiplied by 4 */
+	return_val_if_fail(sx127x_readbyte(sx127x, SX127X_REG_PKTSNRVALUE, &tmp) == 0, -1);
+
+	return (int32_t) (int8_t) tmp;
+}
+
+int32_t sx127x_rssi(sx127x_t *sx127x)
+{
+	uint8_t tmp;
+	int32_t snr = sx127x_snr(sx127x);
+	int32_t rssi;
+
+	return_val_if_fail(sx127x, INT32_MIN);
+
+	/* check if in LF or HF mode */
+	return_val_if_fail(sx127x_readbyte(sx127x, SX127X_REG_PKTSNRVALUE, &tmp) == 0, -1);
+	if(tmp & SX127X_OPMODE_LFON)
+	{
+		rssi = -164;
+	}
+	else
+	{
+		rssi = -157;
+	}
+	/* read raw RSSI of latest received packet */
+	return_val_if_fail(sx127x_readbyte(sx127x, SX127X_REG_PKTSNRVALUE, &tmp) == 0, -1);
+	/* compute RSSI */
+	rssi += (int8_t) tmp;
+	rssi <<= 2; /* rssi *= 4 */
+	if(snr < 0)
+	{
+		rssi += snr;
+	}
+
+	return rssi;
+}
+
+int32_t sx127x_rand(sx127x_t *sx127x)
+{
+	uint8_t tmp;
+
+	return_val_if_fail(sx127x, INT32_MIN);
+
+	/* read raw wideband RSSI */
+	return_val_if_fail(sx127x_readbyte(sx127x, SX127X_REG_RSSIWIDEBAND, &tmp) == 0, -1);
+
+	return tmp;
+}
+
 static int32_t sx127x_writebyte(sx127x_t *sx127x, uint8_t reg, uint8_t byte)
 {
 	uint8_t txdata[2] = { WREG(reg), byte };