From ecdcf078117e9c136d7c562d7baceb1525c3cadc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?King=20K=C3=A9vin?= <kingkevin@cuvoodoo.info>
Date: Thu, 4 May 2017 12:52:50 +0200
Subject: [PATCH] tm1637: fix timing for first bit

---
 lib/led_tm1637.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/lib/led_tm1637.c b/lib/led_tm1637.c
index 8cec959..2d47ac9 100644
--- a/lib/led_tm1637.c
+++ b/lib/led_tm1637.c
@@ -178,7 +178,7 @@ void led_tm1637_setup(void)
 	timer_reset(TIM(LED_TM1637_TIMER)); // reset timer state
 	timer_set_mode(TIM(LED_TM1637_TIMER), TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP); // set timer mode, use undivided timer clock, edge alignment (simple count), and count up
 	timer_set_prescaler(TIM(LED_TM1637_TIMER), 0); // don't prescale to get most precise timing ( 1/(72E6/1/(2**16))=0.91 ms > 0.5 us )
-	timer_set_period(TIM(LED_TM1637_TIMER), 500); // set the clock frequency (emprical value until the signal starts to look bad)
+	timer_set_period(TIM(LED_TM1637_TIMER), 500); // set the clock frequency (500 kHz is the maximum per datasheet, but also because of the bit banging implementation)
 	timer_clear_flag(TIM(LED_TM1637_TIMER), TIM_SR_UIF); // clear flag
 	timer_update_on_overflow(TIM(LED_TM1637_TIMER)); // only use counter overflow as UEV source (use overflow as start time or timeout)
 }
@@ -205,12 +205,12 @@ static bool led_tm1637_write(const uint8_t* data, uint8_t length)
 	}
 
 	// enable timer for signal generation
-	gpio_set_mode(GPIO(LED_TM1637_DIO_PORT), GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO(LED_TM1637_DIO_PIN)); // ensure we can output to sent start condition
 	timer_set_counter(TIM(LED_TM1637_TIMER), 0); // reset timer counter
 	timer_enable_counter(TIM(LED_TM1637_TIMER)); // enable timer to generate timing
 	led_tm1637_tick(); // wait to enforce minimum time since last write
 
 	// send start condition (DIO then CLK low)
+	gpio_set_mode(GPIO(LED_TM1637_DIO_PORT), GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO(LED_TM1637_DIO_PIN)); // ensure we can output to sent start condition
 	gpio_clear(GPIO(LED_TM1637_DIO_PORT), GPIO(LED_TM1637_DIO_PIN)); // put DIO low
 	led_tm1637_tick(); // wait for next tick
 	gpio_clear(GPIO(LED_TM1637_CLK_PORT), GPIO(LED_TM1637_CLK_PIN)); // put CLK low
@@ -218,7 +218,6 @@ static bool led_tm1637_write(const uint8_t* data, uint8_t length)
 	// send data bytes (MSb first)
 	for (uint8_t i=0; i<length; i++) { // send all bytes
 		uint8_t byte = data[i];
-		gpio_set_mode(GPIO(LED_TM1637_DIO_PORT), GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO(LED_TM1637_DIO_PIN)); // switch DIO to output to send bits
 		for (uint8_t b=0; b<8; b++) { // send all bits
 			if (byte&0x1) { // send a 1
 				gpio_set(GPIO(LED_TM1637_DIO_PORT), GPIO(LED_TM1637_DIO_PIN)); // put DIO high
@@ -240,10 +239,10 @@ static bool led_tm1637_write(const uint8_t* data, uint8_t length)
 		}
 		led_tm1637_tick(); // wait for next tick
 		gpio_clear(GPIO(LED_TM1637_CLK_PORT), GPIO(LED_TM1637_CLK_PIN)); // put CLK low
+		gpio_set_mode(GPIO(LED_TM1637_DIO_PORT), GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO(LED_TM1637_DIO_PIN)); // switch DIO back to output
 	}
 
 	// send stop condition
-	gpio_set_mode(GPIO(LED_TM1637_DIO_PORT), GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO(LED_TM1637_DIO_PIN)); // switch DIO to output to send stop condition
 	led_tm1637_tick(); // wait for next tick
 	gpio_set(GPIO(LED_TM1637_CLK_PORT), GPIO(LED_TM1637_CLK_PIN)); // put CLK high
 	led_tm1637_tick(); // wait for next tick