From 8e710f21c4fb50e5918c8e2b5087d7f34b858964 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?King=20K=C3=A9vin?= <kingkevin@cuvoodoo.info>
Date: Wed, 11 Jul 2018 08:20:51 +0200
Subject: [PATCH] USART: put parity LUT in header so others can use it

---
 lib/usart_enhanced.c | 43 +++++++++++++++++++------------------------
 lib/usart_enhanced.h |  6 ++++++
 2 files changed, 25 insertions(+), 24 deletions(-)

diff --git a/lib/usart_enhanced.c b/lib/usart_enhanced.c
index efbcf36..9ca9b47 100644
--- a/lib/usart_enhanced.c
+++ b/lib/usart_enhanced.c
@@ -38,11 +38,7 @@ static enum usart_enhanced_parity_t usart_enhanced_parity[USART_PERIPHERALS_NB];
 /** last enhanced USART parity error status */
 static bool usart_enhanced_parity_errors[USART_PERIPHERALS_NB];
 
-/** know if there is an even number of 1's in a integer
- *  @remark a look-up is a lot faster than making the calculation and doesn't does a lot of (flash) space
- */
-static const bool even_parity_lut[256] = { true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, };
-
+const bool usart_enhanced_even_parity_lut[256] = { true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, true, false, false, true, false, true, true, false, true, false, false, true, false, true, true, false, false, true, true, false, true, false, false, true, };
 
 /** get index of corresponding enhanced USART configurations
  *  @param[in] usart USART peripheral base address
@@ -87,7 +83,7 @@ bool usart_enhanced_config(uint32_t usart, uint8_t databits, enum usart_enhanced
 	usart_enhanced_databits[id] = databits;
 	usart_enhanced_parity[id] = parity;
 	// configure USART peripheral
-	if (8==databits && USART_ENHANCED_PARITY_NONE!=parity) { // the parity bit is additional to the data bits
+	if (8 == databits && USART_ENHANCED_PARITY_NONE != parity) { // the parity bit is additional to the data bits
 		usart_set_databits(usart, 9);
 	} else {
 		usart_set_databits(usart, 8);
@@ -101,26 +97,26 @@ void usart_enhanced_send(uint32_t usart, uint8_t data)
 {
 	/* sanity check */
 	uint8_t id = usart_enhanced_id(usart);
-	if (id>=USART_PERIPHERALS_NB) {
+	if (id >= USART_PERIPHERALS_NB) {
 		return;
 	}
 
-	data &= ~(0xff<<usart_enhanced_databits[id]); // only keep the data bits
+	data &= ~(0xff << usart_enhanced_databits[id]); // only keep the data bits
 	uint16_t output = data; // put value in output buffer
 	switch (usart_enhanced_parity[id]) {
 	case USART_ENHANCED_PARITY_NONE: // a mark is also decoded as idle/stop
 	case USART_ENHANCED_PARITY_MARK:
-		output |= (1<<usart_enhanced_databits[id]); // add idle state
+		output |= (1 << usart_enhanced_databits[id]); // add idle state
 		break;
 	case USART_ENHANCED_PARITY_EVEN:
-		if (!even_parity_lut[data]) {
-			output |= (1<<usart_enhanced_databits[id]);
+		if (!usart_enhanced_even_parity_lut[data]) {
+			output |= (1 << usart_enhanced_databits[id]);
 		}
 		// no need to clear a bit if the parity is even
 		break;
 	case USART_ENHANCED_PARITY_ODD:
-		if (even_parity_lut[data]) {
-			output |= (1<<usart_enhanced_databits[id]);
+		if (usart_enhanced_even_parity_lut[data]) {
+			output |= (1 << usart_enhanced_databits[id]);
 		}
 		// no need to clear a bit if the parity is odd
 		break;
@@ -128,7 +124,7 @@ void usart_enhanced_send(uint32_t usart, uint8_t data)
 		// no need to clear the bit
 		break;
 	}
-	output |= (0xffff<<(usart_enhanced_databits[id]+1)); // set additional bits to idle (high)
+	output |= (0xffff << (usart_enhanced_databits[id] + 1)); // set additional bits to idle (high)
 	usart_send(usart, output); // transmit character
 }
 
@@ -136,14 +132,14 @@ uint8_t usart_enhanced_recv(uint32_t usart)
 {
 	/* sanity check */
 	uint8_t id = usart_enhanced_id(usart);
-	if (id>=USART_PERIPHERALS_NB) {
+	if (id >= USART_PERIPHERALS_NB) {
 		return 0xff;
 	}
 
 	uint16_t input = usart_recv(usart); // read received character (also clears the error flags)
-	input &= ~(0xffff<<(usart_enhanced_databits[id]+1)); // only keep the data bits + parity bit
+	uint8_t data = input & ~(0xffff << usart_enhanced_databits[id]); // only keep the data bits
 	// check the parity
-	uint16_t parity = input&(1<<usart_enhanced_databits[id]); // only keep the parity bit
+	uint16_t parity = input & (1 << usart_enhanced_databits[id]); // only keep the parity bit
 	usart_enhanced_parity_errors[id] = false;
 	switch (usart_enhanced_parity[id]) {
 	case USART_ENHANCED_PARITY_NONE:
@@ -151,16 +147,16 @@ uint8_t usart_enhanced_recv(uint32_t usart)
 		break;
 	case USART_ENHANCED_PARITY_EVEN:
 		if (parity) {
-			usart_enhanced_parity_errors[id] = !even_parity_lut[input&0xff];
+			usart_enhanced_parity_errors[id] = !usart_enhanced_even_parity_lut[data];
 		} else {
-			usart_enhanced_parity_errors[id] = even_parity_lut[input&0xff];
+			usart_enhanced_parity_errors[id] = usart_enhanced_even_parity_lut[data];
 		}
 		break;
 	case USART_ENHANCED_PARITY_ODD:
 		if (parity) {
-			usart_enhanced_parity_errors[id] = even_parity_lut[input&0xff];
+			usart_enhanced_parity_errors[id] = usart_enhanced_even_parity_lut[data];
 		} else {
-			usart_enhanced_parity_errors[id] = !even_parity_lut[input&0xff];
+			usart_enhanced_parity_errors[id] = !usart_enhanced_even_parity_lut[data];
 		}
 		break;
 	case USART_ENHANCED_PARITY_MARK:
@@ -170,15 +166,14 @@ uint8_t usart_enhanced_recv(uint32_t usart)
 		usart_enhanced_parity_errors[id] = parity;
 		break;
 	}
-	input &= ~(0xffff<<(usart_enhanced_databits[id])); // only keep the data bits
-	return input;
+	return data;
 }
 
 bool usart_enhanced_parity_error(uint32_t usart)
 {
 	/* sanity check */
 	uint8_t id = usart_enhanced_id(usart);
-	if (id>=USART_PERIPHERALS_NB) {
+	if (id >= USART_PERIPHERALS_NB) {
 		return false;
 	}
 	return usart_enhanced_parity_errors[id];
diff --git a/lib/usart_enhanced.h b/lib/usart_enhanced.h
index 33f32c7..85bd363 100644
--- a/lib/usart_enhanced.h
+++ b/lib/usart_enhanced.h
@@ -44,6 +44,12 @@ enum usart_enhanced_parity_t {
 	USART_ENHANCED_PARITY_SPACE,
 };
 
+/** know if there is an even number of 1's in a integer
+ *  @note this look up table is only useful for up to 8-bit words, else use __builtin_parity
+ *  @remark a look-up is a lot faster than making the calculation and doesn't use a lot of (flash) memory
+ */
+extern const bool usart_enhanced_even_parity_lut[256];
+
 /** configure enhanced USART
  *  @param[in] usart USART peripheral base address
  *  @param[in] databits word size in bits (5 to 8)