From: Olivier Matz <zer0@droids-corp.org>
Date: Thu, 3 Oct 2013 18:35:38 +0000 (+0200)
Subject: send PPM input on SPI
X-Git-Url: http://git.droids-corp.org/?a=commitdiff_plain;h=0507a9ff89a8cb6be45ec26054d32eb238ec41be;p=protos%2Frc_servos.git

send PPM input on SPI

Signed-off-by: Olivier Matz <zer0@droids-corp.org>
---

diff --git a/main.c b/main.c
index 9c368d5..929ff13 100644
--- a/main.c
+++ b/main.c
@@ -43,6 +43,8 @@ static uint8_t icp_idx = NB_SERVO;
 static uint16_t icp_servos[NB_SERVO];
 static uint16_t icp_prev;
 
+static uint8_t spi_out_idx; /* current byte beeing sent */
+
 #define BYPASS_ENABLE 14
 #define BYPASS_DISABLE 15
 
@@ -62,7 +64,7 @@ static uint16_t icp_prev;
  * Command 14 is to enable bypass mode.
  * Command 15 is to disable bypass mode.
  */
-static union {
+union byte0 {
 	uint8_t u8;
 	struct {
 		/* inverted: little endian */
@@ -70,16 +72,16 @@ static union {
 		uint8_t cmd_num:4;
 		uint8_t zero:1;
 	};
-} byte0;
+};
 
-static union {
+union byte1 {
 	uint8_t u8;
 	struct {
 		/* inverted: little endian */
 		uint8_t val_lsb:7;
 		uint8_t one:1;
 	};
-} byte1;
+};
 
 SIGNAL(TIMER1_COMPA_vect)
 {
@@ -91,12 +93,38 @@ SIGNAL(TIMER1_COMPA_vect)
 static void poll_spi(void)
 {
 	uint8_t c;
+	uint16_t servo;
+	static union byte0 byte0_rx;
+	union byte1 byte1_rx;
+	union byte0 byte0_tx;
+	static union byte1 byte1_tx;
 
 	/* reception complete ? */
 	if (!(SPSR & (1<<SPIF)))
 		return;
 
 	c = SPDR;
+
+	/* prepare next TX */
+
+	if ((spi_out_idx & 1) == 0) {
+		servo = icp_servos[spi_out_idx >> 1];
+		byte0_tx.val_msb = servo >> 7;
+		byte0_tx.cmd_num = (spi_out_idx >> 1) + 1;
+		byte0_tx.zero = 0;
+		byte1_tx.val_lsb = servo & 0x7f;
+		byte1_tx.one = 1;
+		SPDR = byte0_tx.u8;
+	}
+	else {
+		SPDR = byte1_tx.u8;
+	}
+	spi_out_idx ++;
+	if (spi_out_idx >= NB_SERVO)
+		spi_out_idx = 0;
+
+	/* RX */
+
 	if ((rxidx == 0) && (c & 0x80)) {
 		rxidx = 0;
 		return; /* drop */
@@ -107,28 +135,28 @@ static void poll_spi(void)
 	}
 
 	if (rxidx == 0) {
-		byte0.u8 = c;
+		byte0_rx.u8 = c;
 
 		/* command num 0 is ignored */
-		if (byte0.cmd_num == 0)
+		if (byte0_rx.cmd_num == 0)
 			return;
 	}
 	else {
 		uint16_t val;
 
-		byte1.u8 = c;
+		byte1_rx.u8 = c;
 
 		/* process command */
 
-		if (byte0.cmd_num < NB_SERVO+1) {
-			val = (uint16_t)byte0.val_msb << 7;
-			val += byte1.val_lsb;
-			servo_table[byte0.cmd_num-1].command = val;
+		if (byte0_rx.cmd_num < NB_SERVO+1) {
+			val = (uint16_t)byte0_rx.val_msb << 7;
+			val += byte1_rx.val_lsb;
+			servo_table[byte0_rx.cmd_num-1].command = val;
 		}
-		else if (byte0.cmd_num == BYPASS_ENABLE) {
+		else if (byte0_rx.cmd_num == BYPASS_ENABLE) {
 			bypass = 1;
 		}
-		else if (byte0.cmd_num == BYPASS_DISABLE) {
+		else if (byte0_rx.cmd_num == BYPASS_DISABLE) {
 			bypass = 0;
 		}
 	}
@@ -244,8 +272,10 @@ int main(void)
 	TCNT0 = 0;
 	TCCR0B = _BV(CS02) | _BV(CS00);
 
-	/* enable spi (don't set unused MISO as output) */
+	/* enable spi (set MISO as output) */
 	SPCR = _BV(SPE);
+	SPDR = 0;
+	DDRB |= _BV(4);
 
 	sei();