From b224ffdf23c65ec76cddad37c9dcaa68d90cddf9 Mon Sep 17 00:00:00 2001
From: Bart Van Der Meerssche <bart.vandermeerssche@flukso.net>
Date: Sun, 16 Jan 2011 12:00:41 +0100
Subject: [PATCH] [avr] optimize btoh and htob for 8-bit uc

---
 mote/v2/avr/ctrl.c   |  8 ++++----
 mote/v2/avr/encode.h | 27 +++++++++------------------
 mote/v2/avr/main.c   | 12 +++++-------
 3 files changed, 18 insertions(+), 29 deletions(-)

diff --git a/mote/v2/avr/ctrl.c b/mote/v2/avr/ctrl.c
index fb6fb59..54a7175 100644
--- a/mote/v2/avr/ctrl.c
+++ b/mote/v2/avr/ctrl.c
@@ -128,7 +128,7 @@ uint8_t ctrlReadCharFromRxBuffer(uint8_t* pdata)
 	uint8_t high_hex, low_hex;
 
 	if (ctrlGetFromRxBuffer(&high_hex) && ctrlGetFromRxBuffer(&low_hex)) {
-		*pdata = htob(((uint16_t)high_hex << 8) + low_hex);
+		htob(high_hex, low_hex, pdata);
 		return TRUE;
 	}
 	else {
@@ -165,10 +165,10 @@ uint8_t ctrlReadLongFromRxBuffer(uint32_t* pdata)
 
 uint8_t ctrlWriteCharToTxBuffer(uint8_t data)
 {
-	uint16_t hex;
+	uint8_t high_hex, low_hex;
 
-	hex = btoh(data);
-	if (ctrlAddToTxBuffer((uint8_t)(hex >> 8)) && ctrlAddToTxBuffer((uint8_t)hex)) {
+	btoh(data, &high_hex, &low_hex);
+	if (ctrlAddToTxBuffer(high_hex) && ctrlAddToTxBuffer(low_hex)) {
 		return TRUE;
 	}
 	else {
diff --git a/mote/v2/avr/encode.h b/mote/v2/avr/encode.h
index 1c504c5..6b87a5d 100644
--- a/mote/v2/avr/encode.h
+++ b/mote/v2/avr/encode.h
@@ -1,27 +1,18 @@
 #include <stdint.h>
 
 // hex to binary/byte decoding
-static inline uint8_t htob(uint16_t hex)
+static inline void htob(uint8_t high_hex, uint8_t low_hex, uint8_t *pbyte)
 {
-	uint8_t low_hex = (uint8_t) hex;
-	uint8_t high_hex = (uint8_t) (hex >> 8);
-	uint8_t byte;
-
-	byte = (high_hex > 0x40) ? (high_hex & 0x0F) + 9 : high_hex & 0x0F;
-	byte = byte << 4;
-	byte |= (low_hex > 0x40) ? (low_hex & 0x0F) + 9 : low_hex & 0x0F;
-	return byte;
+	*pbyte = (high_hex > 0x40) ? (high_hex & 0x0F) + 9 : high_hex & 0x0F;
+	*pbyte = *pbyte << 4;
+	*pbyte |= (low_hex > 0x40) ? (low_hex & 0x0F) + 9 : low_hex & 0x0F;
 }
 
 // binary/byte to hex encoding
-static inline uint16_t btoh(uint8_t byte)
+static inline void btoh(uint8_t byte, uint8_t *phigh_hex, uint8_t *plow_hex)
 {
-	uint8_t low_nibble = (byte & 0x0F);
-	uint8_t high_nibble = (byte & 0xF0) >> 4;
-	uint16_t hex;
-
-	hex = (high_nibble > 0x09) ? high_nibble - 9 + 0x60 : high_nibble + 0x30;
-	hex = hex << 8;
-	hex |= (low_nibble > 0x09) ? low_nibble - 9 + 0x60 : low_nibble + 0x30;
-	return hex;
+	*plow_hex = byte & 0x0F;
+	*plow_hex = (*plow_hex > 0x09) ? *plow_hex - 9 + 0x60 : *plow_hex + 0x30;
+	*phigh_hex = (byte & 0xF0) >> 4;
+	*phigh_hex = (*phigh_hex > 0x09) ? *phigh_hex - 9 + 0x60 : *phigh_hex + 0x30;
 }
diff --git a/mote/v2/avr/main.c b/mote/v2/avr/main.c
index e9f8fef..8afb83e 100644
--- a/mote/v2/avr/main.c
+++ b/mote/v2/avr/main.c
@@ -60,8 +60,7 @@ volatile struct time_struct time = {0, 0};
 
 ISR(SPI_STC_vect)
 {
-	uint8_t spi_rx, rx, tx; 
-	uint16_t spi_tx;
+	uint8_t spi_rx, spi_tx, rx, tx; 
 
 	DBG_ISR_BEGIN();
 
@@ -82,7 +81,7 @@ ISR(SPI_STC_vect)
 	// are we in Tx mode?
 	if (spi_status & SPI_TRANSMIT) {
 		if (spi_status & SPI_HIGH_HEX) {
-			received_from_spi(spi_high_hex);
+			received_from_spi(spi_high_hex); /* actually low hex ! */
 			spi_status &= ~SPI_HIGH_HEX;
 			return;
 		}
@@ -107,10 +106,9 @@ ISR(SPI_STC_vect)
 			}
 		}
 
-		spi_tx = btoh(tx);
-		spi_high_hex = (uint8_t)spi_tx;
+		btoh(tx, &spi_tx, (uint8_t *)&spi_high_hex); /* actually low hex ! */
 		spi_status |= SPI_HIGH_HEX;
-		received_from_spi((uint8_t)(spi_tx >> 8));
+		received_from_spi(spi_tx);
 		return;
 	}
 
@@ -136,7 +134,7 @@ ISR(SPI_STC_vect)
 			break;
 		default:
 			if (spi_status & SPI_HIGH_HEX) {
-				rx = htob(((uint16_t)spi_high_hex << 8) + spi_rx);
+				htob(spi_high_hex, spi_rx, &rx);
 				uartAddToTxBuffer(rx);
 			}
 			else {