X-Git-Url: http://mj.ucw.cz/gitweb/?a=blobdiff_plain;f=bsb%2Ffirmware%2Fmain.c;h=bb0c48e53bf140ae98ade0e46e9da73180760dbf;hb=37082aba8175e02e86271010ee372d2f34fc6413;hp=e7237e1cf5101cc6f7fdb8b269a34fa5c2773e8e;hpb=d2a47ff7858e03000280d640566c8142578ebf02;p=home-hw.git

diff --git a/bsb/firmware/main.c b/bsb/firmware/main.c
index e7237e1..bb0c48e 100644
--- a/bsb/firmware/main.c
+++ b/bsb/firmware/main.c
@@ -5,6 +5,7 @@
  */
 
 #include "util.h"
+#include "interface.h"
 
 #include <libopencm3/cm3/cortex.h>
 #include <libopencm3/cm3/nvic.h>
@@ -30,12 +31,14 @@ static void clock_init(void)
 	rcc_periph_clock_enable(RCC_GPIOB);
 	rcc_periph_clock_enable(RCC_GPIOC);
 	rcc_periph_clock_enable(RCC_USART1);
+	rcc_periph_clock_enable(RCC_USART3);
 	rcc_periph_clock_enable(RCC_USB);
 
 	rcc_periph_reset_pulse(RST_GPIOA);
 	rcc_periph_reset_pulse(RST_GPIOB);
 	rcc_periph_reset_pulse(RST_GPIOC);
 	rcc_periph_reset_pulse(RST_USART1);
+	rcc_periph_reset_pulse(RST_USART3);
 	rcc_periph_reset_pulse(RST_USB);
 }
 
@@ -56,8 +59,7 @@ static void gpio_init(void)
 
 	// PB10 = TXD3 for BSB
 	// PB11 = RXD3 for BSB
-	// FIXME: TX turned off temporarily
-	// gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_OPENDRAIN, GPIO10);
+	gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_OPENDRAIN, GPIO10);
 	gpio_set_mode(GPIOB, GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, GPIO11);
 }
 
@@ -66,7 +68,7 @@ static void usart_init(void)
 	usart_set_baudrate(USART1, 115200);
 	usart_set_databits(USART1, 8);
 	usart_set_stopbits(USART1, USART_STOPBITS_1);
-	usart_set_mode(USART1, USART_MODE_TX_RX);
+	usart_set_mode(USART1, USART_MODE_TX);
 	usart_set_parity(USART1, USART_PARITY_NONE);
 	usart_set_flow_control(USART1, USART_FLOWCONTROL_NONE);
 
@@ -84,7 +86,7 @@ void sys_tick_handler(void)
 
 static void tick_init(void)
 {
-	systick_set_frequency(1000, 72000000);
+	systick_set_frequency(1000, CPU_CLOCK_MHZ * 1000000);
 	systick_counter_enable();
 	systick_interrupt_enable();
 }
@@ -96,69 +98,359 @@ static void delay_ms(uint ms)
 		;
 }
 
+/*** Random generator ***/
+
+static u32 rng_state;
+
+static u32 random_u32(void)
+{
+	rng_state *= 2654289733;
+	return rng_state;
+}
+
+static void random_init(void)
+{
+	u32 desig[3];
+	desig_get_unique_id(desig);
+	rng_state = desig[0] ^ desig[1] ^ desig[2];
+}
+
 /*** BSB ***/
 
 #define BSB_MAX_SIZE 32
-#define BSB_RX_TIMEOUT 2  // 1-2 ms => 2-4 byte periods of silence
+#define BSB_RX_TIMEOUT 10	// If no byte was received for this time, end the current frame [ms]
+#define BSB_TX_IDLE_LINE 100	// Consider the line idle if no byte was received for this time [ms]
+#define BSB_TX_MAX_ATTEMPTS 3
+#define BSB_TX_WAIT_LOG 8	// base 2 log of pre-frame waiting time in ms
+#define BSB_TX_TIMEOUT 10000	// Total time to transmit a frame including all retries and waiting for reply [ms]
+#define BSB_REPLY_TIMEOUT 1000	// How long to wait for a reply [ms]
+
+#undef DEBUG_BSB
+#ifdef DEBUG_BSB
+#define BSB_DEBUG(x) debug_putc(x)
+#else
+#define BSB_DEBUG(x) do { } while (0)
+#endif
+
+struct bsb_state {
+	byte rx_len;			// Bytes received so far
+	byte rx_led;			// Countdown to turning RX LED off
+	u16 rx_crc;
+	volatile u32 rx_timestamp;	// Last byte received
+
+	byte tx_state;			// TX_STATE_xxx
+	byte tx_len;
+	byte tx_send_index;
+	byte tx_check_index;
+	byte tx_attempts;
+	byte tx_result;			// TX_RESULT_xxx
+	u32 tx_start_timestamp;
+	u32 tx_ticks_to_send;
+	u32 tx_end_timestamp;
+	u32 reply_type_mask;		// Expected reply types (0=no reply)
+
+	byte rx_buf[BSB_MAX_SIZE];
+	byte tx_buf[BSB_MAX_SIZE];
+};
 
-static byte bsb_rx_buf[BSB_MAX_SIZE];
-static byte bsb_rx_len;
-static volatile u32 bsb_rx_timestamp;
+static struct bsb_state bsb;
 
-// Passing received frames to the main loop
-static byte bsb_rx_frame[BSB_MAX_SIZE];
+// Passing received frames and status codes to the main loop
+static byte bsb_rx_status_and_frame[1 + BSB_MAX_SIZE];
 static volatile byte bsb_rx_frame_len;
-static byte bsb_rx_frame_led;
-
-struct bsb_stat {
-	u32 rx_noise;
-	u32 rx_errors;
-	u32 rx_invalid;
-	u32 rx_overruns;
-	u32 rx_timeouts;
+static byte bsb_tx_result;
+
+enum bsb_tx_state {
+	TX_STATE_OFF,
+	TX_STATE_WAITING_FOR_IDLE_LINE,
+	TX_STATE_PRE_PACKET_DELAY,
+	TX_STATE_SENDING,
+	TX_STATE_SENT,
+	TX_STATE_WAITING_FOR_REPLY,
+	TX_STATE_COLLISION,
 };
 
-static struct bsb_stat bsb_stat;
+static struct bsb_stats bsb_stats;
+
+static void bsb_attempt_tx(void);
+
+static u16 bsb_crc_update(u16 crc, byte data)
+{
+	crc = crc ^ (data << 8);
+	for (uint i=0; i<8; i++) {
+		if (crc & 0x8000)
+			crc = (crc << 1) ^ 0x1021;
+		else
+			crc <<= 1;
+	}
+	return crc;
+}
 
 void usart3_isr(void)
 {
 	u32 status = USART_SR(USART3);
 
 	if (status & USART_SR_RXNE) {
-		uint ch = usart_recv(USART3);
-		bsb_rx_timestamp = ms_ticks;
-
-		if (status & (USART_SR_FE | USART_SR_ORE | USART_SR_NE)) {
-			bsb_stat.rx_errors++;
-			bsb_rx_len = 0;
-		} else if (!bsb_rx_len && ch != 0xdc) {
-			// Waiting for start of frame
-			bsb_stat.rx_noise++;
-		} else {
-			bsb_rx_buf[bsb_rx_len++] = ch;
-			if (bsb_rx_len < 4) {
-				// First three bytes: SOF, source addr, destination addr
-			} else if (bsb_rx_len == 4) {
-				// Received length byte
-				if (bsb_rx_buf[3] < 7 || bsb_rx_buf[3] > BSB_MAX_SIZE) {
-					bsb_stat.rx_invalid++;
-					bsb_rx_len = 0;
+		uint ch = ~usart_recv(USART3) & 0xff;
+		bsb.rx_timestamp = ms_ticks;
+#ifdef DEBUG_BSB
+		debug_printf(" %02x", ch);
+#endif
+
+		if (bsb.tx_state == TX_STATE_SENDING) {
+			// We are hearing the echo of a transmitted packet, check it for collisions
+			if (status & (USART_SR_FE | USART_SR_ORE | USART_SR_NE)) {
+				BSB_DEBUG('e');
+				bsb.tx_state = TX_STATE_COLLISION;
+			} else if (ch == bsb.tx_buf[bsb.tx_check_index++]) {
+				if (bsb.tx_check_index >= bsb.tx_len) {
+					BSB_DEBUG('d');
+					bsb.tx_state = TX_STATE_SENT;
 				}
-			} else if (bsb_rx_len == bsb_rx_buf[3]) {
-				// Received a complete frame: pass it to the main loop
-				if (bsb_rx_frame_len) {
-					// The previous one was not sent yet
-					bsb_stat.rx_overruns++;
+			} else {
+				BSB_DEBUG('c');
+				bsb.tx_state = TX_STATE_COLLISION;
+			}
+		} else {
+			// Regular receive
+			if (status & (USART_SR_FE | USART_SR_ORE | USART_SR_NE)) {
+				bsb_stats.rx_errors++;
+				bsb.rx_len = 0;
+			} else if (!bsb.rx_len) {
+				// Start of frame
+				if (ch == 0xdc) {
+					bsb.rx_buf[bsb.rx_len++] = ch;
+					bsb.rx_crc = bsb_crc_update(0, ch);
+					BSB_DEBUG('<');
 				} else {
-					memcpy(bsb_rx_frame, bsb_rx_buf, bsb_rx_buf[3]);
-					barrier();
-					bsb_rx_frame_len = bsb_rx_buf[3];
-					bsb_rx_frame_led = 100;
-					gpio_clear(GPIOB, GPIO1);
+					bsb_stats.rx_noise++;
+					BSB_DEBUG('?');
+				}
+			} else {
+				bsb.rx_buf[bsb.rx_len++] = ch;
+				bsb.rx_crc = bsb_crc_update(bsb.rx_crc, ch);
+				if (bsb.rx_len < 4) {
+					// First three bytes: SOF, source addr, destination addr
+				} else if (bsb.rx_len == 4) {
+					// Received length byte
+					if (bsb.rx_buf[BF_LEN] < 7 || bsb.rx_buf[BF_LEN] > BSB_MAX_SIZE) {
+						bsb_stats.rx_invalid++;
+						bsb.rx_len = 0;
+						BSB_DEBUG('L');
+					}
+				} else if (bsb.rx_len == bsb.rx_buf[BF_LEN]) {
+					// Received a complete frame: check CRC and pass it to the main loop
+					if (bsb.rx_crc) {
+						bsb_stats.rx_bad_crc++;
+						BSB_DEBUG('C');
+					} else {
+						if (bsb_rx_frame_len) {
+							// The previous one was not sent yet
+							bsb_stats.rx_overruns++;
+							BSB_DEBUG('O');
+						} else {
+							bsb_rx_frame_len = bsb.rx_buf[BF_LEN];
+							memcpy(bsb_rx_status_and_frame + 1, bsb.rx_buf, bsb_rx_frame_len);
+							bsb_stats.rx_ok++;
+							BSB_DEBUG('.');
+							// Will match with expected replies in main loop
+						}
+						gpio_clear(GPIOB, GPIO1);
+						bsb.rx_led = 100;
+					}
+					bsb.rx_len = 0;
 				}
 			}
 		}
 	}
+
+	if (status & USART_SR_TXE) {
+		if (bsb.tx_state == TX_STATE_SENDING && bsb.tx_send_index < bsb.tx_len) {
+			BSB_DEBUG('>');
+			usart_send(USART3, bsb.tx_buf[bsb.tx_send_index++] ^ 0xff);
+		} else {
+			usart_disable_tx_interrupt(USART3);
+			// Main loop will be notified by receiving the echo of our frame,
+			// so we do not need to wait for the "transmit complete" flag.
+		}
+	}
+}
+
+static void bsb_rx_step(void)
+{
+	cm_disable_interrupts();
+	barrier();
+	if (bsb.rx_len && ms_ticks - bsb.rx_timestamp >= BSB_RX_TIMEOUT) {
+		bsb.rx_len = 0;
+		bsb_stats.rx_timeouts++;
+		BSB_DEBUG('T');
+	}
+	if (bsb.rx_led) {
+		if (!--bsb.rx_led)
+			gpio_set(GPIOB, GPIO1);
+	}
+	cm_enable_interrupts();
+}
+
+static void bsb_tx_step(void)
+{
+	switch (bsb.tx_state) {
+		case TX_STATE_WAITING_FOR_IDLE_LINE:
+			if (ms_ticks - bsb.rx_timestamp < BSB_TX_IDLE_LINE)
+				return;
+			bsb.tx_state = TX_STATE_PRE_PACKET_DELAY;
+			BSB_DEBUG('i');
+			// Fall thru
+		case TX_STATE_PRE_PACKET_DELAY:
+			if (ms_ticks - bsb.tx_start_timestamp > BSB_TX_TIMEOUT) {
+				bsb.tx_state = TX_STATE_OFF;
+				bsb_tx_result = TX_RESULT_TIMEOUT;
+				bsb_stats.tx_timeouts++;
+				return;
+			}
+			if (ms_ticks - bsb.rx_timestamp < BSB_TX_IDLE_LINE) {
+				bsb.tx_state = TX_STATE_WAITING_FOR_IDLE_LINE;
+				BSB_DEBUG('n');
+				return;
+			}
+			if (--bsb.tx_ticks_to_send)
+				return;
+			BSB_DEBUG('s');
+			bsb.rx_timestamp = ms_ticks;
+			barrier();
+			bsb.tx_state = TX_STATE_SENDING;
+			barrier();
+			usart_enable_tx_interrupt(USART3);
+			return;
+		case TX_STATE_SENDING:
+			// In this state, we can race with the USART interrupt handler
+			cm_disable_interrupts();
+			if (bsb.tx_state == TX_STATE_SENDING && ms_ticks - bsb.rx_timestamp >= BSB_RX_TIMEOUT) {
+				// The echo of our packet was truncated due to collision
+				bsb.tx_state = TX_STATE_COLLISION;
+				BSB_DEBUG('t');
+			}
+			cm_enable_interrupts();
+			return;
+		case TX_STATE_COLLISION:
+			bsb_stats.tx_collisions++;
+			bsb_attempt_tx();
+			return;
+		case TX_STATE_SENT:
+			if (!bsb.reply_type_mask) {
+				// The frame needs no reply => confirm transmission
+				bsb_stats.tx_ok_no_reply++;
+				bsb.tx_state = TX_STATE_OFF;
+				bsb_tx_result = TX_RESULT_OK;
+			} else {
+				bsb.tx_state = TX_STATE_WAITING_FOR_REPLY;
+				bsb.tx_end_timestamp = ms_ticks;
+				BSB_DEBUG('w');
+			}
+			return;
+		case TX_STATE_WAITING_FOR_REPLY:
+			if (ms_ticks - bsb.tx_end_timestamp > BSB_REPLY_TIMEOUT) {
+				// We did not receive a reply. Maybe the request was lost? Re-transmit it.
+				bsb_stats.tx_reply_timeouts++;
+				BSB_DEBUG('t');
+				bsb_attempt_tx();
+			}
+			return;
+		default:
+			;
+	}
+}
+
+static void bsb_attempt_tx(void)
+{
+	if (bsb.tx_attempts++ >= BSB_TX_MAX_ATTEMPTS) {
+		bsb.tx_state = TX_STATE_OFF;
+		bsb_tx_result = TX_RESULT_TOO_MANY_RETRIES;
+		return;
+	}
+
+	bsb.tx_ticks_to_send = (random_u32() | 0x80000000) >> (32 - BSB_TX_WAIT_LOG - (bsb.tx_attempts-1));
+
+	bsb.tx_state = TX_STATE_WAITING_FOR_IDLE_LINE;
+	bsb.tx_send_index = 0;
+	bsb.tx_check_index = 0;
+	debug_printf("TX: Attempt #%u, wait for %u ms\n", bsb.tx_attempts, (uint) bsb.tx_ticks_to_send);
+}
+
+static void bsb_send(byte *buf, uint len)
+{
+	// If a transmit is in progress, declare overrrun
+	if (bsb_tx_result != TX_RESULT_NONE) {
+		bsb_stats.tx_overruns++;
+		return;
+	}
+	if (bsb.tx_state != TX_STATE_OFF) {
+		bsb_stats.tx_overruns++;
+		bsb_tx_result = TX_RESULT_OVERRUN;
+		return;
+	}
+
+	// Check frame validity
+	if (len < 7 || len > BSB_MAX_SIZE || buf[BF_SOF] != 0xdc || buf[BF_LEN] != len) {
+		bsb_stats.tx_rejects++;
+		bsb_tx_result = TX_RESULT_MALFORMED;
+		return;
+	}
+
+	// Detect frame type and prepare expected reply types
+	if (buf[BF_OP] == BSB_OP_QUERY) {
+		// So far, we allow only QUERY frames
+		bsb.reply_type_mask = (1 << BSB_OP_ANSWER) | (1 << BSB_OP_ERROR);
+	} else {
+		bsb_stats.tx_rejects++;
+		bsb_tx_result = TX_RESULT_FORBIDDEN;
+		return;
+	}
+
+	// Fill in source address
+	buf[BF_SRC] = 0x80 + BSB_ADDR_GATEWAY;
+
+	// Calculate CRC
+	u16 crc = 0;
+	for (uint i = 0; i < len - 2; i++)
+		crc = bsb_crc_update(crc, buf[i]);
+	buf[len-2] = crc >> 8;
+	buf[len-1] = crc;
+	debug_printf("TX: Prepared frame: type=%02x dest=%02x len=%u crc=%04x reply=%08x\n", buf[BF_OP], buf[BF_DEST], len, crc, (uint) bsb.reply_type_mask);
+
+	// Queue frame for transmission
+	memcpy(bsb.tx_buf, buf, len);
+	bsb.tx_len = len;
+	bsb.tx_start_timestamp = ms_ticks;
+	bsb.tx_attempts = 0;
+	bsb_attempt_tx();
+
+	// Light the TX LED
+	gpio_clear(GPIOB, GPIO0);
+}
+
+static void bsb_check_reply(void)
+{
+	// Match received frame in bsb_rx_status_and_frame to expected replies
+	// and set the status in byte 0.
+
+	byte *frame = bsb_rx_status_and_frame + 1;
+	// XXX: This might be executed too fast, so we can still be in TX_STATE_SENT
+	if (bsb.tx_state == TX_STATE_WAITING_FOR_REPLY || bsb.tx_state == TX_STATE_SENT) {
+		if (frame[BF_DEST] == BSB_ADDR_GATEWAY &&
+		    frame[BF_SRC] == bsb.tx_buf[BF_DEST] ^ 0x80 &&
+		    frame[BF_OP] < 32 &&
+		    bsb.reply_type_mask & (1 << frame[BF_OP])) {
+			debug_printf("BSB: Matched reply\n");
+			bsb.tx_state = TX_STATE_OFF;
+			bsb_stats.tx_ok_replied++;
+			bsb_rx_status_and_frame[0] = TX_RESULT_OK;
+			gpio_set(GPIOB, GPIO0);		// Turn the TX LED off
+			return;
+		}
+	}
+
+	bsb_rx_status_and_frame[0] = TX_RESULT_NONE;
 }
 
 static void bsb_init(void)
@@ -179,6 +471,20 @@ static void bsb_init(void)
 
 static usbd_device *usbd_dev;
 
+enum usb_string {
+	STR_MANUFACTURER = 1,
+	STR_PRODUCT,
+	STR_SERIAL,
+};
+
+static char usb_serial_number[13];
+
+static const char *usb_strings[] = {
+	"United Computer Wizards",
+	"BSB Gateway",
+	usb_serial_number,
+};
+
 static const struct usb_device_descriptor device = {
 	.bLength = USB_DT_DEVICE_SIZE,
 	.bDescriptorType = USB_DT_DEVICE,
@@ -187,23 +493,25 @@ static const struct usb_device_descriptor device = {
 	.bDeviceSubClass = 0,
 	.bDeviceProtocol = 0,
 	.bMaxPacketSize0 = 64,
-	.idVendor = 0x4242,
-	.idProduct = 0x0003,
-	.bcdDevice = 0x0200,
-	.iManufacturer = 1,
-	.iProduct = 2,
-	.iSerialNumber = 3,
+	.idVendor = BSB_USB_VENDOR,
+	.idProduct = BSB_USB_PRODUCT,
+	.bcdDevice = BSB_USB_VERSION,
+	.iManufacturer = STR_MANUFACTURER,
+	.iProduct = STR_PRODUCT,
+	.iSerialNumber = STR_SERIAL,
 	.bNumConfigurations = 1,
 };
 
 static const struct usb_endpoint_descriptor endpoints[] = {{
+	// Bulk end-point for sending frames to BSB
 	.bLength = USB_DT_ENDPOINT_SIZE,
 	.bDescriptorType = USB_DT_ENDPOINT,
-	.bEndpointAddress = 0x81,
+	.bEndpointAddress = 0x01,
 	.bmAttributes = USB_ENDPOINT_ATTR_BULK,
 	.wMaxPacketSize = 64,
 	.bInterval = 1,
 },{
+	// Interrupt end-point for receiving frames from BSB
 	.bLength = USB_DT_ENDPOINT_SIZE,
 	.bDescriptorType = USB_DT_ENDPOINT,
 	.bEndpointAddress = 0x82,
@@ -269,16 +577,8 @@ static const struct usb_config_descriptor config = {
 	.interface = ifaces,
 };
 
-static char usb_serial_number[13];
-
-static const char *usb_strings[] = {
-	"United Computer Wizards",
-	"BSB Gateway",
-	usb_serial_number,
-};
-
 static byte usb_configured;
-static byte usb_rx_pending;
+static byte usb_ep82_pending;
 static uint8_t usbd_control_buffer[64];
 
 static enum usbd_request_return_codes control_cb(
@@ -292,9 +592,9 @@ static enum usbd_request_return_codes control_cb(
 		return USBD_REQ_NOTSUPP;
 
 	// We support reading of statistics via control requests
-	debug_printf("USB: Control request: Read statistics\n");
-	uint n = MIN(*len, sizeof(bsb_stat));
-	memcpy(*buf, (char *) &bsb_stat, n);
+	debug_printf("USB: Reading statistics\n");
+	uint n = MIN(*len, sizeof(bsb_stats));
+	memcpy(*buf, (char *) &bsb_stats, n);
 	*len = n;
 
 	return USBD_REQ_HANDLED;
@@ -321,34 +621,36 @@ static enum usbd_request_return_codes dfu_control_cb(usbd_device *dev UNUSED,
 	return USBD_REQ_HANDLED;
 }
 
-static void ep81_cb(usbd_device *dev, uint8_t ep UNUSED)
+static void ep01_cb(usbd_device *dev, uint8_t ep UNUSED)
 {
-	byte buf[4];
-	put_u32_be(buf, ms_ticks);
-	usbd_ep_write_packet(dev, 0x81, buf, sizeof(buf));
-	debug_printf("USB: Bulk write\n");
+	// We received a frame from the USB host
+	byte buf[64];
+	uint len = usbd_ep_read_packet(dev, 0x01, buf, sizeof(buf));
+	debug_printf("USB: Host sent %u bytes\n", len);
+	bsb_send(buf, len);
 }
 
-static void rx_cb(usbd_device *dev UNUSED, uint8_t ep UNUSED)
+static void ep82_cb(usbd_device *dev UNUSED, uint8_t ep UNUSED)
 {
-	// Received packet passed through interrupt end-point
-	debug_printf("USB: RX EP done\n");
-	usb_rx_pending = 0;
+	// The frame was accepted by the USB host
+	debug_printf("USB: Interrupt done\n");
+	usb_ep82_pending = 0;
 }
 
 static void set_config_cb(usbd_device *dev, uint16_t wValue UNUSED)
 {
-	usbd_register_control_callback(dev,
+	usbd_register_control_callback(
+		dev,
 		USB_REQ_TYPE_VENDOR,
 		USB_REQ_TYPE_TYPE,
 		control_cb);
-	usbd_register_control_callback(dev,
+	usbd_register_control_callback(
+		dev,
 		USB_REQ_TYPE_CLASS | USB_REQ_TYPE_INTERFACE,
 		USB_REQ_TYPE_TYPE | USB_REQ_TYPE_RECIPIENT,
 		dfu_control_cb);
-	usbd_ep_setup(dev, 0x81, USB_ENDPOINT_ATTR_BULK, 64, ep81_cb);
-	usbd_ep_setup(dev, 0x82, USB_ENDPOINT_ATTR_BULK, 64, rx_cb);
-	ep81_cb(dev, 0);
+	usbd_ep_setup(dev, 0x01, USB_ENDPOINT_ATTR_BULK, 64, ep01_cb);
+	usbd_ep_setup(dev, 0x82, USB_ENDPOINT_ATTR_INTERRUPT, 64, ep82_cb);
 	usb_configured = 1;
 }
 
@@ -356,6 +658,7 @@ static void reset_cb(void)
 {
 	debug_printf("USB: Reset\n");
 	usb_configured = 0;
+	usb_ep82_pending = 0;
 }
 
 static volatile bool usb_event_pending;
@@ -379,7 +682,7 @@ static void usb_init(void)
 	// Simulate USB disconnect
 	gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_OPENDRAIN, GPIO11 | GPIO12);
 	gpio_clear(GPIOA, GPIO11 | GPIO12);
-	delay_ms(1000);
+	delay_ms(100);
 
 	usbd_dev = usbd_init(
 		&st_usbfs_v1_usb_driver,
@@ -404,19 +707,20 @@ int main(void)
 	tick_init();
 	usart_init();
 	desig_get_unique_id_as_dfu(usb_serial_number);
+	random_init();
 
-	debug_printf("Hello, kitty!\n");
+	debug_printf("Hail, Lord Damian! Thy BSB interface is ready.\n");
 
 	bsb_init();
 	usb_init();
 
-	u32 last_ds_step = 0;
+	u32 last_blink = 0;
+	u32 last_step = 0;
 
 	for (;;) {
-		if (ms_ticks - last_ds_step >= 100) {
+		if (ms_ticks - last_blink >= 100) {
 			debug_led_toggle();
-			gpio_toggle(GPIOB, GPIO0);
-			last_ds_step = ms_ticks;
+			last_blink = ms_ticks;
 		}
 
 		if (usb_event_pending) {
@@ -427,31 +731,33 @@ int main(void)
 		}
 
 		if (usb_configured) {
-			// Passing of received packets to USB
-			if (!usb_rx_pending) {
+			// Passing of received frames to USB
+			if (!usb_ep82_pending) {
 				if (bsb_rx_frame_len) {
+					// Received frame, possibly marked as reply
 					barrier();
-					usbd_ep_write_packet(usbd_dev, 0x82, bsb_rx_frame, bsb_rx_frame_len);
-					usb_rx_pending = 1;
+					bsb_check_reply();
+					usbd_ep_write_packet(usbd_dev, 0x82, bsb_rx_status_and_frame, 1 + bsb_rx_frame_len);
+					usb_ep82_pending = 1;
 					barrier();
 					bsb_rx_frame_len = 0;
-					debug_printf("USB: RX started\n");
+					debug_printf("USB: Sending frame to interrupt EP\n");
+				} else if (bsb_tx_result != TX_RESULT_NONE) {
+					// Only a transmission result
+					usbd_ep_write_packet(usbd_dev, 0x82, &bsb_tx_result, 1);
+					usb_ep82_pending = 1;
+					gpio_set(GPIOB, GPIO0);		// Turn the TX LED off
+					debug_printf("USB: Sending status %u to interrupt EP\n", bsb_tx_result);
+					bsb_tx_result = TX_RESULT_NONE;
 				}
 			}
 		}
 
-		// Packet timeouts
-		cm_disable_interrupts();
-		barrier();
-		if (bsb_rx_len && (bsb_rx_timestamp - ms_ticks) >= BSB_RX_TIMEOUT) {
-			bsb_rx_len = 0;
-			bsb_stat.rx_timeouts++;
-		}
-		if (bsb_rx_frame_led) {
-			if (!--bsb_rx_frame_led)
-				gpio_set(GPIOB, GPIO1);
+		if (ms_ticks != last_step) {
+			last_step = ms_ticks;
+			bsb_rx_step();
+			bsb_tx_step();
 		}
-		cm_enable_interrupts();
 
 		wait_for_interrupt();
 	}