From d0cdde2a4d3983780d4dd08e6970dccd1b37a073 Mon Sep 17 00:00:00 2001
From: Martin Mares <mj@ucw.cz>
Date: Sat, 11 Apr 2020 15:53:05 +0200
Subject: [PATCH] DMX: USB interface

---
 dmx/firmware/main.c | 50 +++++++++++++++++++++++++++++++++------------
 1 file changed, 37 insertions(+), 13 deletions(-)

diff --git a/dmx/firmware/main.c b/dmx/firmware/main.c
index cc0b826..f2b89f7 100644
--- a/dmx/firmware/main.c
+++ b/dmx/firmware/main.c
@@ -98,11 +98,16 @@ static void delay_ms(uint ms)
 
 /*** DMX ***/
 
+#define DMX_MAX_PACKET_SIZE 64
+
 static volatile byte dmx_state;
-static byte dmx_packet[64];
+static byte dmx_packet[DMX_MAX_PACKET_SIZE];
 static byte dmx_pos, dmx_len;
 
-#define DEBUG_DMX
+static byte dmx_next_packet[DMX_MAX_PACKET_SIZE];
+static byte dmx_next_len;
+
+#undef DEBUG_DMX
 #ifdef DEBUG_DMX
 #define DMX_DEBUG(ch) debug_putc(ch)
 #else
@@ -122,7 +127,7 @@ static void dmx_init(void)
 {
 	usart_set_baudrate(USART3, 250000);
 	usart_set_databits(USART3, 8);
-	usart_set_stopbits(USART3, USART_STOPBITS_1);
+	usart_set_stopbits(USART3, USART_STOPBITS_2);
 	usart_set_mode(USART3, USART_MODE_TX);
 	usart_set_parity(USART3, USART_PARITY_NONE);
 	usart_set_flow_control(USART3, USART_FLOWCONTROL_NONE);
@@ -137,6 +142,10 @@ static void dmx_init(void)
 	timer_one_shot_mode(TIM3);
 	timer_enable_irq(TIM3, TIM_DIER_UIE);
 	nvic_enable_irq(NVIC_TIM3_IRQ);
+
+	// Until we get data from USB, send "turn everything off" packets
+	memset(dmx_next_packet, 0, DMX_MAX_PACKET_SIZE);
+	dmx_next_len = DMX_MAX_PACKET_SIZE;
 }
 
 void tim3_isr(void)
@@ -189,9 +198,9 @@ void usart3_isr(void)
 		// Transfer of the last byte is complete, but we have to wait
 		// before the start of the next packet: minimum time between two
 		// breaks must be at least 1204 μs. We already sent a 200μs break,
-		// 200μs mark, and dmx_len 40μs data slots.
+		// 200μs mark, and dmx_len 44μs data slots.
 		USART_CR1(USART3) &= ~USART_CR1_TCIE;
-		uint sent = 200 + 200 + 40*dmx_len;
+		uint sent = 200 + 200 + 44*dmx_len;
 		if (sent < 1300) {
 			DMX_DEBUG('g');
 			dmx_state = DMX_STATE_GAP;
@@ -210,13 +219,10 @@ static void dmx_send(void)
 	if (dmx_state != DMX_STATE_IDLE)
 		return;
 
-	dmx_packet[0] = 0;
-	dmx_packet[1] = 0xff;	// warm
-	dmx_packet[2] = 0xff;	// cold
-	dmx_packet[3] = 0;
-	dmx_packet[4] = 0;
+	if (!dmx_len)
+		return;
+
 	dmx_pos = 0;
-	dmx_len = 5;
 
 	// Send break for 200 μs
 	DMX_DEBUG('<');
@@ -358,9 +364,9 @@ static enum usbd_request_return_codes dfu_control_cb(usbd_device *dev UNUSED,
 static void ep01_cb(usbd_device *dev, uint8_t ep UNUSED)
 {
 	// We received a frame from the USB host
-	byte buf[64];
-	uint len = usbd_ep_read_packet(dev, 0x01, buf, sizeof(buf));
+	uint len = usbd_ep_read_packet(dev, 0x01, dmx_next_packet, DMX_MAX_PACKET_SIZE);
 	debug_printf("USB: Host sent %u bytes\n", len);
+	dmx_next_len = len;
 }
 
 static void set_config_cb(usbd_device *dev, uint16_t wValue UNUSED)
@@ -433,6 +439,7 @@ int main(void)
 	dmx_init();
 
 	u32 last_blink = 0;
+	u32 last_send = 0;
 
 	for (;;) {
 		if (ms_ticks - last_blink >= 100) {
@@ -448,6 +455,23 @@ int main(void)
 			nvic_enable_irq(NVIC_USB_LP_CAN_RX0_IRQ);
 		}
 
+		if (dmx_state == DMX_STATE_IDLE) {
+			if (dmx_next_len) {
+				// We have a new packet to send
+				debug_printf("Sending new packet: %d bytes\n", dmx_next_len);
+				memcpy(dmx_packet, dmx_next_packet, dmx_next_len);
+				dmx_len = dmx_next_len;
+				dmx_next_len = 0;
+				dmx_send();
+				last_send = ms_ticks;
+			} else if (ms_ticks - last_send >= 100) {
+				// Re-send every 100 ms
+				// debug_printf("Re-send: %d bytes\n", dmx_len);
+				dmx_send();
+				last_send = ms_ticks;
+			}
+		}
+
 		wait_for_interrupt();
 	}
 
-- 
2.39.2