From fc0fb4f8d54c52ed6db4ca2deb8bf6d02d4800ff Mon Sep 17 00:00:00 2001
From: John Tsiombikas <nuclear@member.fsf.org>
Date: Wed, 3 Mar 2021 04:13:12 +0200
Subject: [PATCH] holding SCL low after setting my saturation value is rather
 crude, but works. I'll keep looking for a better solution.

---
 main.c |   42 ++++++++++++++++++++++++++----------------
 1 file changed, 26 insertions(+), 16 deletions(-)

diff --git a/main.c b/main.c
index 8e3a5c9..aa593da 100644
--- a/main.c
+++ b/main.c
@@ -22,7 +22,8 @@ enum {
 #define I2C_STOP()	(TWCR = TWINT_BIT | TWSTO_BIT | TWEN_BIT | TWIE_BIT)
 #define I2C_WRITE()	(TWCR = TWINT_BIT | TWEN_BIT | TWIE_BIT)
 
-unsigned char i2c_addr, i2c_subaddr, i2c_mode;
+unsigned char i2c_addr, i2c_subaddr;
+volatile unsigned char i2c_mode;
 int i2c_seq, i2c_ndata;
 unsigned char *i2c_data;
 int i2c_retry_delay;
@@ -44,6 +45,8 @@ volatile int evq_wr, evq_rd;
 static char input[64];
 static unsigned char inp_cidx;
 
+static unsigned char data[8];
+
 static void proc_cmd(char *input);
 void i2c_write(unsigned char addr, unsigned char subaddr, int ndata, unsigned char *data);
 
@@ -51,7 +54,7 @@ int main(void)
 {
 	/* tri-state everything and disable pullups */
 	DDRB = 1;	/* B0: activity LED */
-	DDRC = 0;
+	DDRC = 0x20; /* SCL output so we can hold the clock low when disabling i2c */
 	DDRD = 0;
 	PORTB = 0;
 	PORTC = 0;
@@ -59,10 +62,9 @@ int main(void)
 
 	TWBR = 10;		/* 10 with 1x prescaler should make it about 100khz */
 	TWSR = 0;		/* prescaler 1x */
-	TWAR = 0xff;
+	TWAR = 0x8a;		/* let's monitor for commands going to the jungle */
+	TWAMR = 0;
 	TWCR = (1 << TWEN) | (1 << TWIE); /* enable i2c, don't ack, enable intr */
-	TWAR = 0xff;
-	TWAMR = 0;//0xff;	/* match all addresses to monitor the bus */
 
 	i2c_mode = I2C_IDLE;
 
@@ -72,7 +74,7 @@ int main(void)
 	printf("Starting i2c hack\n");
 
 	for(;;) {
-		uint16_t val = 0xffff;
+		//uint16_t val = 0xffff;
 
 		if(have_input()) {
 			int c = getchar();
@@ -89,6 +91,7 @@ int main(void)
 		}
 
 		/* read from queue and send over the serial port */
+		/*
 		cli();
 		if(evq_wr != evq_rd) {
 			val = evq[evq_rd];
@@ -99,14 +102,18 @@ int main(void)
 		if(val != 0xffff) {
 			printf("s(%u): %x\n", (unsigned int)(val >> 8), (unsigned int)(val & 0xff));
 		}
+		*/
+		/*
+		_delay_us(100);
+		data[0] = 0x3f;
+		i2c_write(0x8a, 0x1c, 1, data);
+		*/
 	}
 	return 0;
 }
 
 static void proc_cmd(char *input)
 {
-	unsigned char data[8];
-
 	if(strcmp(input, "rgb") == 0) {
 		printf("OK sending RGB switch command\n");
 
@@ -137,10 +144,15 @@ static void proc_cmd(char *input)
 		i2c_write(0x8a, 0x10, 1, data);
 		printf("OK unzoom\n");
 
-	} else if(strcmp(input, "sat") == 0) {
-		data[0] = 0x3f;
-		i2c_write(0x8a, 0x1c, 1, data);
+	} else if(memcmp(input, "sat", 3) == 0) {
 		printf("OK saturate\n");
+		data[0] = atoi(input + 3);
+		if(data[0] <= 0 || data[0] > 0x3f) {
+			data[0] = 0x1f;
+		}
+		i2c_write(0x8a, 0x1c, 1, data);
+		while(i2c_mode);
+		TWCR = 0;
 
 	} else if(strcmp(input, "abort") == 0) {
 		if(i2c_mode != I2C_IDLE) {
@@ -158,7 +170,6 @@ static void proc_cmd(char *input)
 
 void i2c_write(unsigned char addr, unsigned char subaddr, int ndata, unsigned char *data)
 {
-	printf("i2c: write %x (sub: %x)\n", addr, subaddr);
 	i2c_addr = addr & 0xfe;
 	i2c_subaddr = subaddr;
 	i2c_mode = I2C_MASTER_SEND;
@@ -300,9 +311,9 @@ ISR(TWI_vect)
 		default:
 			break;
 		}
-		/* append data to input queue */
-		/*
-		TWCR |= 1 << TWINT;
+
+		/* append data to the event queue */
+		TWCR = TWINT_BIT | TWEN_BIT | TWIE_BIT;
 
 		evq[evq_wr] = ev;
 		evq_wr = (evq_wr + 1) & (EVQ_SIZE - 1);
@@ -311,6 +322,5 @@ ISR(TWI_vect)
 		}
 
 		PORTB = 1;
-		*/
 	}
 }
-- 
1.7.10.4