X-Git-Url: http://mj.ucw.cz/gitweb/?a=blobdiff_plain;f=bsb%2Ffirmware%2Fmain.c;h=bb0c48e53bf140ae98ade0e46e9da73180760dbf;hb=37082aba8175e02e86271010ee372d2f34fc6413;hp=fda60d40f416e6c4f035a0dad88f585b8043282e;hpb=a692aefc44560a674b2057c6166c9d6b673cf779;p=home-hw.git

diff --git a/bsb/firmware/main.c b/bsb/firmware/main.c
index fda60d4..bb0c48e 100644
--- a/bsb/firmware/main.c
+++ b/bsb/firmware/main.c
@@ -5,17 +5,24 @@
  */
 
 #include "util.h"
+#include "interface.h"
 
+#include <libopencm3/cm3/cortex.h>
 #include <libopencm3/cm3/nvic.h>
 #include <libopencm3/cm3/systick.h>
-#include <libopencm3/stm32/rcc.h>		// FIXME: Clean up
+#include <libopencm3/cm3/scb.h>
+#include <libopencm3/stm32/rcc.h>
+#include <libopencm3/stm32/desig.h>
 #include <libopencm3/stm32/gpio.h>
 #include <libopencm3/stm32/timer.h>
 #include <libopencm3/stm32/usart.h>
+#include <libopencm3/usb/dfu.h>
 #include <libopencm3/usb/usbd.h>
 
 #include <string.h>
 
+/*** Hardware init ***/
+
 static void clock_init(void)
 {
 	rcc_clock_setup_in_hse_8mhz_out_72mhz();
@@ -24,28 +31,52 @@ 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);
 }
 
 static void gpio_init(void)
 {
 	// PA9 = TXD1 for debugging console
-	gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO9);
-
 	// PA10 = RXD1 for debugging console
+	gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO9);
 	gpio_set_mode(GPIOA, GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, GPIO10);
 
 	// PC13 = BluePill LED
 	gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO13);
 	gpio_clear(GPIOC, GPIO13);
+
+	// PB0 = yellow LED*, PB1 = green LED*
+	gpio_set_mode(GPIOB, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_OPENDRAIN, GPIO0 | GPIO1);
+	gpio_set(GPIOB, GPIO0 | GPIO1);
+
+	// PB10 = TXD3 for BSB
+	// PB11 = RXD3 for BSB
+	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);
 }
 
+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);
+	usart_set_parity(USART1, USART_PARITY_NONE);
+	usart_set_flow_control(USART1, USART_FLOWCONTROL_NONE);
+
+	usart_enable(USART1);
+}
+
+/*** System ticks ***/
+
 static volatile u32 ms_ticks;
 
 void sys_tick_handler(void)
@@ -55,7 +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();
 }
@@ -67,19 +98,394 @@ static void delay_ms(uint ms)
 		;
 }
 
-static void usart_init(void)
+/*** Random generator ***/
+
+static u32 rng_state;
+
+static u32 random_u32(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_parity(USART1, USART_PARITY_NONE);
-	usart_set_flow_control(USART1, USART_FLOWCONTROL_NONE);
+	rng_state *= 2654289733;
+	return rng_state;
+}
 
-	usart_enable(USART1);
+static void random_init(void)
+{
+	u32 desig[3];
+	desig_get_unique_id(desig);
+	rng_state = desig[0] ^ desig[1] ^ desig[2];
 }
 
-static const struct usb_device_descriptor dev = {
+/*** BSB ***/
+
+#define BSB_MAX_SIZE 32
+#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 struct bsb_state bsb;
+
+// 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_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_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) & 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 {
+				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 {
+					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)
+{
+	usart_set_baudrate(USART3, 4800);
+	usart_set_databits(USART3, 9);
+	usart_set_stopbits(USART3, USART_STOPBITS_1);
+	usart_set_mode(USART3, USART_MODE_TX_RX);
+	usart_set_parity(USART3, USART_PARITY_ODD);
+	usart_set_flow_control(USART3, USART_FLOWCONTROL_NONE);
+
+	usart_enable(USART3);
+	nvic_enable_irq(NVIC_USART3_IRQ);
+	usart_enable_rx_interrupt(USART3);
+}
+
+/*** USB ***/
+
+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,
 	.bcdUSB = 0x0200,
@@ -87,23 +493,25 @@ static const struct usb_device_descriptor dev = {
 	.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,
@@ -125,16 +533,43 @@ static const struct usb_interface_descriptor iface = {
 	.endpoint = endpoints,
 };
 
+static const struct usb_dfu_descriptor dfu_function = {
+	.bLength = sizeof(struct usb_dfu_descriptor),
+	.bDescriptorType = DFU_FUNCTIONAL,
+	.bmAttributes = USB_DFU_CAN_DOWNLOAD | USB_DFU_WILL_DETACH,
+	.wDetachTimeout = 255,
+	.wTransferSize = 1024,
+	.bcdDFUVersion = 0x0100,
+};
+
+static const struct usb_interface_descriptor dfu_iface = {
+	.bLength = USB_DT_INTERFACE_SIZE,
+	.bDescriptorType = USB_DT_INTERFACE,
+	.bInterfaceNumber = 1,
+	.bAlternateSetting = 0,
+	.bNumEndpoints = 0,
+	.bInterfaceClass = 0xFE,
+	.bInterfaceSubClass = 1,
+	.bInterfaceProtocol = 1,
+	.iInterface = 0,
+
+	.extra = &dfu_function,
+	.extralen = sizeof(dfu_function),
+};
+
 static const struct usb_interface ifaces[] = {{
 	.num_altsetting = 1,
 	.altsetting = &iface,
+}, {
+	.num_altsetting = 1,
+	.altsetting = &dfu_iface,
 }};
 
 static const struct usb_config_descriptor config = {
 	.bLength = USB_DT_CONFIGURATION_SIZE,
 	.bDescriptorType = USB_DT_CONFIGURATION,
 	.wTotalLength = 0,
-	.bNumInterfaces = 1,
+	.bNumInterfaces = 2,
 	.bConfigurationValue = 1,
 	.iConfiguration = 0,
 	.bmAttributes = 0x80,
@@ -142,55 +577,80 @@ static const struct usb_config_descriptor config = {
 	.interface = ifaces,
 };
 
-static const char *usb_strings[] = {
-	"United Computer Wizards",
-	"BSB Gateway",
-	"1",
-};
-
 static byte usb_configured;
+static byte usb_ep82_pending;
 static uint8_t usbd_control_buffer[64];
 
-static enum usbd_request_return_codes control_cb(usbd_device *usbd_dev,
+static enum usbd_request_return_codes control_cb(
+	usbd_device *dev UNUSED,
 	struct usb_setup_data *req,
 	uint8_t **buf,
 	uint16_t *len,
-	void (**complete)(usbd_device *usbd_dev, struct usb_setup_data *req) UNUSED)
+	void (**complete)(usbd_device *dev, struct usb_setup_data *req) UNUSED)
 {
 	if (req->bmRequestType != 0xc0 || req->bRequest != 0x00)
 		return USBD_REQ_NOTSUPP;
 
-	(void) usbd_dev;
-	(void) buf;
-	(void) len;
-	(void) complete;
-	debug_printf("USB: Control request\n");
+	// We support reading of statistics via control requests
+	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;
+}
+
+static void dfu_detach_complete(usbd_device *dev UNUSED, struct usb_setup_data *req UNUSED)
+{
+	// Reset to bootloader, which implements the rest of DFU
+	debug_printf("Switching to DFU\n");
+	debug_flush();
+	scb_reset_core();
+}
 
-	byte *b = *buf;
-	b[0] = 0x12;
-	b[1] = 0x34;
-	b[2] = 0x56;
-	b[3] = 0x78;
-	if (*len > 4)
-		*len = 4;
+static enum usbd_request_return_codes dfu_control_cb(usbd_device *dev UNUSED,
+	struct usb_setup_data *req,
+	uint8_t **buf UNUSED,
+	uint16_t *len UNUSED,
+	void (**complete)(usbd_device *dev, struct usb_setup_data *req))
+{
+	if (req->bmRequestType != 0x21 || req->bRequest != DFU_DETACH)
+		return USBD_REQ_NOTSUPP;
 
+	*complete = dfu_detach_complete;
 	return USBD_REQ_HANDLED;
 }
 
-static void ep81_cb(usbd_device *usbd_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(usbd_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 set_config_cb(usbd_device *usbd_dev, uint16_t wValue UNUSED)
+static void ep82_cb(usbd_device *dev UNUSED, uint8_t ep UNUSED)
 {
-	usbd_register_control_callback(usbd_dev, USB_REQ_TYPE_VENDOR, USB_REQ_TYPE_TYPE, control_cb);
-	usbd_ep_setup(usbd_dev, 0x81, USB_ENDPOINT_ATTR_BULK, 64, ep81_cb);
-	usbd_ep_setup(usbd_dev, 0x82, USB_ENDPOINT_ATTR_BULK, 64, NULL);
-	ep81_cb(usbd_dev, 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,
+		USB_REQ_TYPE_VENDOR,
+		USB_REQ_TYPE_TYPE,
+		control_cb);
+	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, 0x01, USB_ENDPOINT_ATTR_BULK, 64, ep01_cb);
+	usbd_ep_setup(dev, 0x82, USB_ENDPOINT_ATTR_INTERRUPT, 64, ep82_cb);
 	usb_configured = 1;
 }
 
@@ -198,41 +658,108 @@ static void reset_cb(void)
 {
 	debug_printf("USB: Reset\n");
 	usb_configured = 0;
+	usb_ep82_pending = 0;
 }
 
+static volatile bool usb_event_pending;
+
+void usb_lp_can_rx0_isr(void)
+{
+	/*
+	 *  We handle USB in the main loop to avoid race conditions between
+	 *  USB interrupts and other code. However, we need an interrupt to
+	 *  up the main loop from sleep.
+	 *
+	 *  We set up only the low-priority ISR, because high-priority ISR handles
+	 *  only double-buffered bulk transfers and isochronous transfers.
+	 */
+	nvic_disable_irq(NVIC_USB_LP_CAN_RX0_IRQ);
+	usb_event_pending = 1;
+}
+
+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(100);
+
+	usbd_dev = usbd_init(
+		&st_usbfs_v1_usb_driver,
+		&device,
+		&config,
+		usb_strings,
+		ARRAY_SIZE(usb_strings),
+		usbd_control_buffer,
+		sizeof(usbd_control_buffer)
+	);
+	usbd_register_reset_callback(usbd_dev, reset_cb);
+	usbd_register_set_config_callback(usbd_dev, set_config_cb);
+	usb_event_pending = 1;
+}
+
+/*** Main ***/
+
 int main(void)
 {
 	clock_init();
 	gpio_init();
 	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");
 
-	// 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);
+	bsb_init();
+	usb_init();
 
-	usbd_device *usbd_dev = usbd_init(&st_usbfs_v1_usb_driver, &dev, &config, usb_strings, 3, usbd_control_buffer, sizeof(usbd_control_buffer));
-	usbd_register_reset_callback(usbd_dev, reset_cb);
-	usbd_register_set_config_callback(usbd_dev, set_config_cb);
-	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();
-			last_ds_step = ms_ticks;
-			if (usb_configured) {
-				byte x[4];
-				put_u32_be(x, ms_ticks);
-				usbd_ep_write_packet(usbd_dev, 0x82, x, 4);
+			last_blink = ms_ticks;
+		}
+
+		if (usb_event_pending) {
+			usbd_poll(usbd_dev);
+			usb_event_pending = 0;
+			nvic_clear_pending_irq(NVIC_USB_LP_CAN_RX0_IRQ);
+			nvic_enable_irq(NVIC_USB_LP_CAN_RX0_IRQ);
+		}
+
+		if (usb_configured) {
+			// Passing of received frames to USB
+			if (!usb_ep82_pending) {
+				if (bsb_rx_frame_len) {
+					// Received frame, possibly marked as reply
+					barrier();
+					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: 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;
+				}
 			}
 		}
 
-		// XXX: libopencm3 usbd does not use interrupts at the moment, need to poll...
-		// wait_for_interrupt();
-		usbd_poll(usbd_dev);
+		if (ms_ticks != last_step) {
+			last_step = ms_ticks;
+			bsb_rx_step();
+			bsb_tx_step();
+		}
+
+		wait_for_interrupt();
 	}
 
 	return 0;