altos/stm32f1: More stm32f103 work
[fw/altos] / src / stm32f1 / ao_usb_stm.c
diff --git a/src/stm32f1/ao_usb_stm.c b/src/stm32f1/ao_usb_stm.c
new file mode 100644 (file)
index 0000000..3d632dd
--- /dev/null
@@ -0,0 +1,1172 @@
+/*
+ * Copyright © 2023 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include "ao.h"
+#include "ao_usb.h"
+#include "ao_product.h"
+
+#define USB_DEBUG      0
+#define USB_DEBUG_DATA 0
+#define USB_ECHO       0
+
+#ifndef USE_USB_STDIO
+#define USE_USB_STDIO  1
+#endif
+
+#if USE_USB_STDIO
+#define AO_USB_OUT_SLEEP_ADDR  (&ao_stdin_ready)
+#else
+#define AO_USB_OUT_SLEEP_ADDR  (&ao_usb_out_avail)
+#endif
+
+#if USB_DEBUG
+#define debug(format, args...) printf(format, ## args);
+#else
+#define debug(format, args...)
+#endif
+
+#if USB_DEBUG_DATA
+#define debug_data(format, args...)    printf(format, ## args);
+#else
+#define debug_data(format, args...)
+#endif
+
+struct ao_usb_setup {
+       uint8_t         dir_type_recip;
+       uint8_t         request;
+       uint16_t        value;
+       uint16_t        index;
+       uint16_t        length;
+} ao_usb_setup;
+
+static uint8_t         ao_usb_ep0_state;
+
+/* Pending EP0 IN data */
+static const uint8_t   *ao_usb_ep0_in_data;    /* Remaining data */
+static uint8_t                 ao_usb_ep0_in_len;      /* Remaining amount */
+
+/* Temp buffer for smaller EP0 in data */
+static uint8_t ao_usb_ep0_in_buf[2];
+
+/* Pending EP0 OUT data */
+static uint8_t *ao_usb_ep0_out_data;
+static uint8_t         ao_usb_ep0_out_len;
+
+/*
+ * Objects allocated in special USB memory
+ */
+
+/* Buffer description tables */
+static union stm_usb_bdt       *ao_usb_bdt;
+/* USB address of end of allocated storage */
+static uint16_t        ao_usb_sram_addr;
+
+/* Pointer to ep0 tx/rx buffers in USB memory */
+static uint32_t        *ao_usb_ep0_tx_buffer;
+static uint32_t        *ao_usb_ep0_rx_buffer;
+
+/* Pointer to bulk data tx/rx buffers in USB memory */
+static uint32_t        *ao_usb_in_tx_buffer;
+static uint32_t        *ao_usb_out_rx_buffer;
+
+/* System ram shadow of USB buffer; writing individual bytes is
+ * too much of a pain (sigh) */
+static uint8_t ao_usb_tx_buffer[AO_USB_IN_SIZE];
+static uint8_t ao_usb_tx_count;
+
+static uint8_t ao_usb_rx_buffer[AO_USB_OUT_SIZE];
+static uint8_t ao_usb_rx_count, ao_usb_rx_pos;
+
+/*
+ * End point register indices
+ */
+
+#define AO_USB_CONTROL_EPR     0
+#define AO_USB_INT_EPR         1
+#define AO_USB_OUT_EPR         2
+#define AO_USB_IN_EPR          3
+
+/* Marks when we don't need to send an IN packet.
+ * This happens only when the last IN packet is not full,
+ * otherwise the host will expect to keep seeing packets.
+ * Send a zero-length packet as required
+ */
+static uint8_t ao_usb_in_flushed;
+
+/* Marks when we have delivered an IN packet to the hardware
+ * and it has not been received yet. ao_sleep on this address
+ * to wait for it to be delivered.
+ */
+static uint8_t ao_usb_in_pending;
+
+/* Marks when an OUT packet has been received by the hardware
+ * but not pulled to the shadow buffer.
+ */
+static uint8_t ao_usb_out_avail;
+uint8_t                ao_usb_running;
+static uint8_t ao_usb_configuration;
+
+#define AO_USB_EP0_GOT_RESET   1
+#define AO_USB_EP0_GOT_SETUP   2
+#define AO_USB_EP0_GOT_RX_DATA 4
+#define AO_USB_EP0_GOT_TX_ACK  8
+
+static uint8_t ao_usb_ep0_receive;
+static uint8_t ao_usb_address;
+static uint8_t ao_usb_address_pending;
+
+static inline uint32_t set_toggle(uint32_t     current_value,
+                                  uint32_t     mask,
+                                  uint32_t     desired_value)
+{
+       return (current_value ^ desired_value) & mask;
+}
+
+static inline uint32_t *ao_usb_packet_buffer_addr(uint16_t sram_addr)
+{
+       return (uint32_t *) (((void *) ((uint8_t *) stm_usb_sram + 2 * sram_addr)));
+}
+
+static inline uint32_t ao_usb_epr_stat_rx(uint32_t epr) {
+       return (epr >> STM_USB_EPR_STAT_RX) & STM_USB_EPR_STAT_RX_MASK;
+}
+
+static inline uint32_t ao_usb_epr_stat_tx(uint32_t epr) {
+       return (epr >> STM_USB_EPR_STAT_TX) & STM_USB_EPR_STAT_TX_MASK;
+}
+
+static inline uint32_t ao_usb_epr_ctr_rx(uint32_t epr) {
+       return (epr >> STM_USB_EPR_CTR_RX) & 1;
+}
+
+static inline uint32_t ao_usb_epr_ctr_tx(uint32_t epr) {
+       return (epr >> STM_USB_EPR_CTR_TX) & 1;
+}
+
+static inline uint32_t ao_usb_epr_setup(uint32_t epr) {
+       return (epr >> STM_USB_EPR_SETUP) & 1;
+}
+
+static inline uint32_t ao_usb_epr_dtog_rx(uint32_t epr) {
+       return (epr >> STM_USB_EPR_DTOG_RX) & 1;
+}
+
+static inline uint32_t ao_usb_epr_dtog_tx(uint32_t epr) {
+       return (epr >> STM_USB_EPR_DTOG_TX) & 1;
+}
+
+/*
+ * Set current device address and mark the
+ * interface as active
+ */
+static void
+ao_usb_set_address(uint8_t address)
+{
+       debug("ao_usb_set_address %02x\n", address);
+       stm_usb.daddr = (1 << STM_USB_DADDR_EF) | address;
+       ao_usb_address_pending = 0;
+}
+
+/*
+ * Write these values to preserve register contents under HW changes
+ */
+
+#define STM_USB_EPR_INVARIANT  ((1 << STM_USB_EPR_CTR_RX) |            \
+                                (STM_USB_EPR_DTOG_RX_WRITE_INVARIANT << STM_USB_EPR_DTOG_RX) | \
+                                (STM_USB_EPR_STAT_RX_WRITE_INVARIANT << STM_USB_EPR_STAT_RX) | \
+                                (1 << STM_USB_EPR_CTR_TX) |            \
+                                (STM_USB_EPR_DTOG_TX_WRITE_INVARIANT << STM_USB_EPR_DTOG_TX) | \
+                                (STM_USB_EPR_STAT_TX_WRITE_INVARIANT << STM_USB_EPR_STAT_TX))
+
+#define STM_USB_EPR_INVARIANT_MASK     ((1 << STM_USB_EPR_CTR_RX) |    \
+                                        (STM_USB_EPR_DTOG_RX_MASK << STM_USB_EPR_DTOG_RX) | \
+                                        (STM_USB_EPR_STAT_RX_MASK << STM_USB_EPR_STAT_RX) | \
+                                        (1 << STM_USB_EPR_CTR_TX) |    \
+                                        (STM_USB_EPR_DTOG_TX_MASK << STM_USB_EPR_DTOG_TX) | \
+                                        (STM_USB_EPR_STAT_TX_MASK << STM_USB_EPR_STAT_TX))
+
+/*
+ * These bits are purely under sw control, so preserve them in the
+ * register by re-writing what was read
+ */
+#define STM_USB_EPR_PRESERVE_MASK      ((STM_USB_EPR_EP_TYPE_MASK << STM_USB_EPR_EP_TYPE) | \
+                                        (1 << STM_USB_EPR_EP_KIND) |   \
+                                        (STM_USB_EPR_EA_MASK << STM_USB_EPR_EA))
+
+#define TX_DBG 0
+#define RX_DBG 0
+
+#if TX_DBG
+#define _tx_dbg0(msg) _dbg(__LINE__,msg,0)
+#define _tx_dbg1(msg,value) _dbg(__LINE__,msg,value)
+#else
+#define _tx_dbg0(msg)
+#define _tx_dbg1(msg,value)
+#endif
+
+#if RX_DBG
+#define _rx_dbg0(msg) _dbg(__LINE__,msg,0)
+#define _rx_dbg1(msg,value) _dbg(__LINE__,msg,value)
+#else
+#define _rx_dbg0(msg)
+#define _rx_dbg1(msg,value)
+#endif
+
+#if TX_DBG || RX_DBG
+static void _dbg(int line, char *msg, uint32_t value);
+#endif
+
+/*
+ * Set the state of the specified endpoint register to a new
+ * value. This is tricky because the bits toggle where the new
+ * value is one, and we need to write invariant values in other
+ * spots of the register. This hardware is strange...
+ */
+static void
+_ao_usb_set_stat_tx(int ep, uint32_t stat_tx)
+{
+       uint32_t        epr_write, epr_old;
+
+       _tx_dbg1("set_stat_tx top", stat_tx);
+       epr_old = epr_write = stm_usb.epr[ep];
+       epr_write &= STM_USB_EPR_PRESERVE_MASK;
+       epr_write |= STM_USB_EPR_INVARIANT;
+       epr_write |= set_toggle(epr_old,
+                             STM_USB_EPR_STAT_TX_MASK << STM_USB_EPR_STAT_TX,
+                             stat_tx << STM_USB_EPR_STAT_TX);
+       stm_usb.epr[ep] = epr_write;
+       _tx_dbg1("set_stat_tx bottom", epr_write);
+}
+
+static void
+ao_usb_set_stat_tx(int ep, uint32_t stat_tx)
+{
+       ao_arch_block_interrupts();
+       _ao_usb_set_stat_tx(ep, stat_tx);
+       ao_arch_release_interrupts();
+}
+
+static void
+_ao_usb_set_stat_rx(int ep, uint32_t stat_rx) {
+       uint32_t        epr_write, epr_old;
+
+       epr_write = epr_old = stm_usb.epr[ep];
+       epr_write &= STM_USB_EPR_PRESERVE_MASK;
+       epr_write |= STM_USB_EPR_INVARIANT;
+       epr_write |= set_toggle(epr_old,
+                             STM_USB_EPR_STAT_RX_MASK << STM_USB_EPR_STAT_RX,
+                             stat_rx << STM_USB_EPR_STAT_RX);
+       stm_usb.epr[ep] = epr_write;
+}
+
+static void
+ao_usb_set_stat_rx(int ep, uint32_t stat_rx) {
+       ao_arch_block_interrupts();
+       _ao_usb_set_stat_rx(ep, stat_rx);
+       ao_arch_release_interrupts();
+}
+
+/*
+ * Set just endpoint 0, for use during startup
+ */
+
+static void
+ao_usb_init_ep(uint8_t ep, uint32_t addr, uint32_t type, uint32_t stat_rx, uint32_t stat_tx)
+{
+       uint32_t                epr;
+       ao_arch_block_interrupts();
+       epr = stm_usb.epr[ep];
+       epr = ((0 << STM_USB_EPR_CTR_RX) |
+              (epr & (1 << STM_USB_EPR_DTOG_RX)) |
+              set_toggle(epr,
+                         (STM_USB_EPR_STAT_RX_MASK << STM_USB_EPR_STAT_RX),
+                         (stat_rx << STM_USB_EPR_STAT_RX)) |
+              (type << STM_USB_EPR_EP_TYPE) |
+              (0 << STM_USB_EPR_EP_KIND) |
+              (0 << STM_USB_EPR_CTR_TX) |
+              (epr & (1 << STM_USB_EPR_DTOG_TX)) |
+              set_toggle(epr,
+                         (STM_USB_EPR_STAT_TX_MASK << STM_USB_EPR_STAT_TX),
+                         (stat_tx << STM_USB_EPR_STAT_TX)) |
+              (addr << STM_USB_EPR_EA));
+       stm_usb.epr[ep] = epr;
+       ao_arch_release_interrupts();
+       debug ("writing epr[%d] 0x%08x wrote 0x%08x\n",
+              ep, epr, stm_usb.epr[ep]);
+}
+
+static void
+ao_usb_set_ep0(void)
+{
+       uint8_t e;
+
+       ao_usb_sram_addr = 0;
+
+       /* buffer table is at the start of USB memory */
+       stm_usb.btable = 0;
+       ao_usb_bdt = (void *) stm_usb_sram;
+
+       ao_usb_sram_addr += 8 * STM_USB_BDT_SIZE;
+
+       /* Set up EP 0 - a Control end point with 32 bytes of in and out buffers */
+
+       ao_usb_bdt[0].single.addr_tx = ao_usb_sram_addr;
+       ao_usb_bdt[0].single.count_tx = 0;
+       ao_usb_ep0_tx_buffer = ao_usb_packet_buffer_addr(ao_usb_sram_addr);
+       ao_usb_sram_addr += AO_USB_CONTROL_SIZE;
+
+       ao_usb_bdt[0].single.addr_rx = ao_usb_sram_addr;
+       ao_usb_bdt[0].single.count_rx = ((1 << STM_USB_BDT_COUNT_RX_BL_SIZE) |
+                                 (((AO_USB_CONTROL_SIZE / 32) - 1) << STM_USB_BDT_COUNT_RX_NUM_BLOCK));
+       ao_usb_ep0_rx_buffer = ao_usb_packet_buffer_addr(ao_usb_sram_addr);
+       ao_usb_sram_addr += AO_USB_CONTROL_SIZE;
+
+       ao_usb_init_ep(AO_USB_CONTROL_EPR, AO_USB_CONTROL_EP,
+                      STM_USB_EPR_EP_TYPE_CONTROL,
+                      STM_USB_EPR_STAT_RX_VALID,
+                      STM_USB_EPR_STAT_TX_NAK);
+
+       /* Clear all of the other endpoints */
+       for (e = 1; e < 8; e++) {
+               ao_usb_init_ep(e, 0,
+                              STM_USB_EPR_EP_TYPE_CONTROL,
+                              STM_USB_EPR_STAT_RX_DISABLED,
+                              STM_USB_EPR_STAT_TX_DISABLED);
+       }
+
+       ao_usb_set_address(0);
+
+       ao_usb_running = 0;
+
+       /* Reset our internal state
+        */
+
+       ao_usb_ep0_state = AO_USB_EP0_IDLE;
+
+       ao_usb_ep0_in_data = NULL;
+       ao_usb_ep0_in_len = 0;
+
+       ao_usb_ep0_out_data = 0;
+       ao_usb_ep0_out_len = 0;
+}
+
+static void
+ao_usb_set_configuration(void)
+{
+       debug ("ao_usb_set_configuration\n");
+
+       /* Set up the INT end point */
+       ao_usb_bdt[AO_USB_INT_EPR].single.addr_tx = ao_usb_sram_addr;
+       ao_usb_bdt[AO_USB_INT_EPR].single.count_tx = 0;
+       ao_usb_in_tx_buffer = ao_usb_packet_buffer_addr(ao_usb_sram_addr);
+       ao_usb_sram_addr += AO_USB_INT_SIZE;
+
+       ao_usb_init_ep(AO_USB_INT_EPR,
+                      AO_USB_INT_EP,
+                      STM_USB_EPR_EP_TYPE_INTERRUPT,
+                      STM_USB_EPR_STAT_RX_DISABLED,
+                      STM_USB_EPR_STAT_TX_NAK);
+
+       /* Set up the OUT end point */
+       ao_usb_bdt[AO_USB_OUT_EPR].single.addr_rx = ao_usb_sram_addr;
+       ao_usb_bdt[AO_USB_OUT_EPR].single.count_rx = ((1 << STM_USB_BDT_COUNT_RX_BL_SIZE) |
+                                                     (((AO_USB_OUT_SIZE / 32) - 1) << STM_USB_BDT_COUNT_RX_NUM_BLOCK));
+       ao_usb_out_rx_buffer = ao_usb_packet_buffer_addr(ao_usb_sram_addr);
+       ao_usb_sram_addr += AO_USB_OUT_SIZE;
+
+       ao_usb_init_ep(AO_USB_OUT_EPR,
+                      AO_USB_OUT_EP,
+                      STM_USB_EPR_EP_TYPE_BULK,
+                      STM_USB_EPR_STAT_RX_VALID,
+                      STM_USB_EPR_STAT_TX_DISABLED);
+
+       /* Set up the IN end point */
+       ao_usb_bdt[AO_USB_IN_EPR].single.addr_tx = ao_usb_sram_addr;
+       ao_usb_bdt[AO_USB_IN_EPR].single.count_tx = 0;
+       ao_usb_in_tx_buffer = ao_usb_packet_buffer_addr(ao_usb_sram_addr);
+       ao_usb_sram_addr += AO_USB_IN_SIZE;
+
+       ao_usb_init_ep(AO_USB_IN_EPR,
+                      AO_USB_IN_EP,
+                      STM_USB_EPR_EP_TYPE_BULK,
+                      STM_USB_EPR_STAT_RX_DISABLED,
+                      STM_USB_EPR_STAT_TX_NAK);
+
+       ao_usb_in_flushed = 0;
+       ao_usb_in_pending = 0;
+       ao_wakeup(&ao_usb_in_pending);
+
+       ao_usb_out_avail = 0;
+       ao_usb_configuration = 0;
+
+       ao_usb_running = 1;
+       ao_wakeup(&ao_usb_running);
+}
+
+static uint16_t        control_count;
+static uint16_t int_count;
+static uint16_t        in_count;
+static uint16_t        out_count;
+static uint16_t        reset_count;
+
+/* The USB memory holds 16 bit values on 32 bit boundaries
+ * and must be accessed only in 32 bit units. Sigh.
+ */
+
+static inline void
+ao_usb_write_byte(uint8_t byte, uint32_t *base, uint16_t offset)
+{
+       base += offset >> 1;
+       if (offset & 1) {
+               *base = (*base & 0xff) | ((uint32_t) byte << 8);
+       } else {
+               *base = (*base & 0xff00) | byte;
+       }
+}
+
+static inline void
+ao_usb_write_short(uint16_t data, uint32_t *base, uint16_t offset)
+{
+       base[offset>>1] = data;
+}
+
+static void
+ao_usb_write(const uint8_t *src, uint32_t *base, uint16_t bytes)
+{
+       uint16_t offset = 0;
+       if (!bytes)
+               return;
+       while (bytes >= 2) {
+               debug_data (" %02x %02x", src[0], src[1]);
+               ao_usb_write_short((uint16_t) ((uint16_t) (src[1] << 8) | (uint16_t) src[0]), base, offset);
+               offset += 2;
+               src += 2;
+               bytes -= 2;
+       }
+       if (bytes) {
+               debug_data (" %02x", src[0]);
+               ao_usb_write_byte(*src, base, offset);
+       }
+}
+
+static inline uint8_t
+ao_usb_read_byte(uint32_t *base, uint16_t offset)
+{
+       base += offset >> 1;
+       if (offset & 1)
+               return (*base >> 8) & 0xff;
+       else
+               return *base & 0xff;
+}
+
+static inline uint16_t
+ao_usb_read_short(uint32_t *base, uint16_t offset)
+{
+       return (uint16_t) (base[offset>>1]);
+}
+
+static void
+ao_usb_read(uint8_t *dst, uint32_t *base, uint16_t offset, uint16_t bytes)
+{
+       if (!bytes)
+               return;
+       if (offset & 1) {
+               *dst++ = ao_usb_read_byte(base, offset++);
+               debug_data (" %02x", dst[-1]);
+               bytes--;
+       }
+       while (bytes >= 2) {
+               uint16_t        s = ao_usb_read_short(base, offset);
+               dst[0] = (uint8_t) s;
+               dst[1] = (uint8_t) (s >> 8);
+               debug_data (" %02x %02x", dst[0], dst[1]);
+               offset += 2;
+               dst += 2;
+               bytes -= 2;
+       }
+       if (bytes) {
+               *dst = ao_usb_read_byte(base, offset);
+               debug_data (" %02x", dst[0]);
+       }
+}
+
+/* Send an IN data packet */
+static void
+ao_usb_ep0_flush(void)
+{
+       uint8_t this_len;
+
+       /* Check to see if the endpoint is still busy */
+       if (ao_usb_epr_stat_tx(stm_usb.epr[0]) == STM_USB_EPR_STAT_TX_VALID) {
+               debug("EP0 not accepting IN data\n");
+               return;
+       }
+
+       this_len = ao_usb_ep0_in_len;
+       if (this_len > AO_USB_CONTROL_SIZE)
+               this_len = AO_USB_CONTROL_SIZE;
+
+       if (this_len < AO_USB_CONTROL_SIZE)
+               ao_usb_ep0_state = AO_USB_EP0_IDLE;
+
+       ao_usb_ep0_in_len -= this_len;
+
+       debug_data ("Flush EP0 len %d:", this_len);
+       ao_usb_write(ao_usb_ep0_in_data, ao_usb_ep0_tx_buffer, this_len);
+       debug_data ("\n");
+       ao_usb_ep0_in_data += this_len;
+
+       /* Mark the endpoint as TX valid to send the packet */
+       ao_usb_bdt[AO_USB_CONTROL_EPR].single.count_tx = this_len;
+       ao_usb_set_stat_tx(AO_USB_CONTROL_EPR, STM_USB_EPR_STAT_TX_VALID);
+       debug ("queue tx. epr 0 now %08x\n", stm_usb.epr[AO_USB_CONTROL_EPR]);
+}
+
+/* Read data from the ep0 OUT fifo */
+static void
+ao_usb_ep0_fill(void)
+{
+       uint16_t        len = ao_usb_bdt[0].single.count_rx & STM_USB_BDT_COUNT_RX_COUNT_RX_MASK;
+
+       if (len > ao_usb_ep0_out_len)
+               len = ao_usb_ep0_out_len;
+       ao_usb_ep0_out_len -= (uint8_t) len;
+
+       /* Pull all of the data out of the packet */
+       debug_data ("Fill EP0 len %d:", len);
+       ao_usb_read(ao_usb_ep0_out_data, ao_usb_ep0_rx_buffer, 0, len);
+       debug_data ("\n");
+       ao_usb_ep0_out_data += len;
+
+       /* ACK the packet */
+       ao_usb_set_stat_rx(0, STM_USB_EPR_STAT_RX_VALID);
+}
+
+static void
+ao_usb_ep0_in_reset(void)
+{
+       ao_usb_ep0_in_data = ao_usb_ep0_in_buf;
+       ao_usb_ep0_in_len = 0;
+}
+
+static void
+ao_usb_ep0_in_queue_byte(uint8_t a)
+{
+       if (ao_usb_ep0_in_len < sizeof (ao_usb_ep0_in_buf))
+               ao_usb_ep0_in_buf[ao_usb_ep0_in_len++] = a;
+}
+
+static void
+ao_usb_ep0_in_set(const uint8_t *data, uint8_t len)
+{
+       ao_usb_ep0_in_data = data;
+       ao_usb_ep0_in_len = len;
+}
+
+static void
+ao_usb_ep0_out_set(uint8_t *data, uint8_t len)
+{
+       ao_usb_ep0_out_data = data;
+       ao_usb_ep0_out_len = len;
+}
+
+static void
+ao_usb_ep0_in_start(uint16_t max)
+{
+       /* Don't send more than asked for */
+       if (ao_usb_ep0_in_len > max)
+               ao_usb_ep0_in_len = (uint8_t) max;
+       ao_usb_ep0_flush();
+}
+
+struct ao_usb_line_coding ao_usb_line_coding = {115200, 0, 0, 8};
+
+/* Walk through the list of descriptors and find a match
+ */
+static void
+ao_usb_get_descriptor(uint16_t value, uint16_t length)
+{
+       const uint8_t           *descriptor;
+       uint8_t         type = (uint8_t) (value >> 8);
+       uint8_t         index = (uint8_t) value;
+
+       descriptor = ao_usb_descriptors;
+       while (descriptor[0] != 0) {
+               if (descriptor[1] == type && index-- == 0) {
+                       uint8_t len;
+                       if (type == AO_USB_DESC_CONFIGURATION)
+                               len = descriptor[2];
+                       else
+                               len = descriptor[0];
+                       if (len > length)
+                               len = (uint8_t) length;
+                       ao_usb_ep0_in_set(descriptor, len);
+                       break;
+               }
+               descriptor += descriptor[0];
+       }
+}
+
+static void
+ao_usb_ep0_setup(void)
+{
+       /* Pull the setup packet out of the fifo */
+       ao_usb_ep0_out_set((uint8_t *) &ao_usb_setup, 8);
+       ao_usb_ep0_fill();
+       if (ao_usb_ep0_out_len != 0) {
+               debug ("invalid setup packet length\n");
+               return;
+       }
+
+       if ((ao_usb_setup.dir_type_recip & AO_USB_DIR_IN) || ao_usb_setup.length == 0)
+               ao_usb_ep0_state = AO_USB_EP0_DATA_IN;
+       else
+               ao_usb_ep0_state = AO_USB_EP0_DATA_OUT;
+
+       ao_usb_ep0_in_reset();
+
+       switch(ao_usb_setup.dir_type_recip & AO_USB_SETUP_TYPE_MASK) {
+       case AO_USB_TYPE_STANDARD:
+               debug ("Standard setup packet\n");
+               switch(ao_usb_setup.dir_type_recip & AO_USB_SETUP_RECIP_MASK) {
+               case AO_USB_RECIP_DEVICE:
+                       debug ("Device setup packet\n");
+                       switch(ao_usb_setup.request) {
+                       case AO_USB_REQ_GET_STATUS:
+                               debug ("get status\n");
+                               ao_usb_ep0_in_queue_byte(0);
+                               ao_usb_ep0_in_queue_byte(0);
+                               break;
+                       case AO_USB_REQ_SET_ADDRESS:
+                               debug ("set address %d\n", ao_usb_setup.value);
+                               ao_usb_address = (uint8_t) ao_usb_setup.value;
+                               ao_usb_address_pending = 1;
+                               break;
+                       case AO_USB_REQ_GET_DESCRIPTOR:
+                               debug ("get descriptor %d\n", ao_usb_setup.value);
+                               ao_usb_get_descriptor(ao_usb_setup.value, ao_usb_setup.length);
+                               break;
+                       case AO_USB_REQ_GET_CONFIGURATION:
+                               debug ("get configuration %d\n", ao_usb_configuration);
+                               ao_usb_ep0_in_queue_byte(ao_usb_configuration);
+                               break;
+                       case AO_USB_REQ_SET_CONFIGURATION:
+                               ao_usb_configuration = (uint8_t) ao_usb_setup.value;
+                               debug ("set configuration %d\n", ao_usb_configuration);
+                               ao_usb_set_configuration();
+                               break;
+                       }
+                       break;
+               case AO_USB_RECIP_INTERFACE:
+                       debug ("Interface setup packet\n");
+                       switch(ao_usb_setup.request) {
+                       case AO_USB_REQ_GET_STATUS:
+                               ao_usb_ep0_in_queue_byte(0);
+                               ao_usb_ep0_in_queue_byte(0);
+                               break;
+                       case AO_USB_REQ_GET_INTERFACE:
+                               ao_usb_ep0_in_queue_byte(0);
+                               break;
+                       case AO_USB_REQ_SET_INTERFACE:
+                               break;
+                       }
+                       break;
+               case AO_USB_RECIP_ENDPOINT:
+                       debug ("Endpoint setup packet\n");
+                       switch(ao_usb_setup.request) {
+                       case AO_USB_REQ_GET_STATUS:
+                               ao_usb_ep0_in_queue_byte(0);
+                               ao_usb_ep0_in_queue_byte(0);
+                               break;
+                       }
+                       break;
+               }
+               break;
+       case AO_USB_TYPE_CLASS:
+               debug ("Class setup packet\n");
+               switch (ao_usb_setup.request) {
+               case AO_USB_SET_LINE_CODING:
+                       debug ("set line coding\n");
+                       ao_usb_ep0_out_set((uint8_t *) &ao_usb_line_coding, 7);
+                       break;
+               case AO_USB_GET_LINE_CODING:
+                       debug ("get line coding\n");
+                       ao_usb_ep0_in_set((const uint8_t *) &ao_usb_line_coding, 7);
+                       break;
+               case AO_USB_SET_CONTROL_LINE_STATE:
+                       break;
+               }
+               break;
+       }
+
+       /* If we're not waiting to receive data from the host,
+        * queue an IN response
+        */
+       if (ao_usb_ep0_state == AO_USB_EP0_DATA_IN)
+               ao_usb_ep0_in_start(ao_usb_setup.length);
+}
+
+static void
+ao_usb_ep0_handle(uint8_t receive)
+{
+       ao_usb_ep0_receive = 0;
+       if (receive & AO_USB_EP0_GOT_RESET) {
+               debug ("\treset\n");
+               ao_usb_set_ep0();
+               return;
+       }
+       if (receive & AO_USB_EP0_GOT_SETUP) {
+               debug ("\tsetup\n");
+               ao_usb_ep0_setup();
+       }
+       if (receive & AO_USB_EP0_GOT_RX_DATA) {
+               debug ("\tgot rx data\n");
+               if (ao_usb_ep0_state == AO_USB_EP0_DATA_OUT) {
+                       ao_usb_ep0_fill();
+                       if (ao_usb_ep0_out_len == 0) {
+                               ao_usb_ep0_state = AO_USB_EP0_DATA_IN;
+                               ao_usb_ep0_in_start(0);
+                       }
+               }
+       }
+       if (receive & AO_USB_EP0_GOT_TX_ACK) {
+               debug ("\tgot tx ack\n");
+
+#if HAS_FLIGHT && AO_USB_FORCE_IDLE
+               ao_flight_force_idle = 1;
+#endif
+               /* Wait until the IN packet is received from addr 0
+                * before assigning our local address
+                */
+               if (ao_usb_address_pending)
+                       ao_usb_set_address(ao_usb_address);
+               if (ao_usb_ep0_state == AO_USB_EP0_DATA_IN)
+                       ao_usb_ep0_flush();
+       }
+}
+
+void
+stm_usb_lp_isr(void)
+{
+       uint32_t        istr = stm_usb.istr;
+
+       if (istr & (1 << STM_USB_ISTR_CTR)) {
+               uint8_t         ep = istr & STM_USB_ISTR_EP_ID_MASK;
+               uint32_t        epr, epr_write;
+
+               /* Preserve the SW write bits, don't mess with most HW writable bits,
+                * clear the CTR_RX and CTR_TX bits
+                */
+               epr = stm_usb.epr[ep];
+               epr_write = epr;
+               epr_write &= STM_USB_EPR_PRESERVE_MASK;
+               epr_write |= STM_USB_EPR_INVARIANT;
+               epr_write &= ~(1UL << STM_USB_EPR_CTR_RX);
+               epr_write &= ~(1UL << STM_USB_EPR_CTR_TX);
+               stm_usb.epr[ep] = epr_write;
+
+               switch (ep) {
+               case 0:
+                       ++control_count;
+                       if (ao_usb_epr_ctr_rx(epr)) {
+                               if (ao_usb_epr_setup(epr))
+                                       ao_usb_ep0_receive |= AO_USB_EP0_GOT_SETUP;
+                               else
+                                       ao_usb_ep0_receive |= AO_USB_EP0_GOT_RX_DATA;
+                       }
+                       if (ao_usb_epr_ctr_tx(epr))
+                               ao_usb_ep0_receive |= AO_USB_EP0_GOT_TX_ACK;
+                       ao_usb_ep0_handle(ao_usb_ep0_receive);
+                       break;
+               case AO_USB_OUT_EPR:
+                       ++out_count;
+                       if (ao_usb_epr_ctr_rx(epr)) {
+                               _rx_dbg1("RX ISR", epr);
+                               ao_usb_out_avail = 1;
+                               _rx_dbg0("out avail set");
+                               ao_wakeup(AO_USB_OUT_SLEEP_ADDR);
+                               _rx_dbg0("stdin awoken");
+                       }
+                       break;
+               case AO_USB_IN_EPR:
+                       ++in_count;
+                       _tx_dbg1("TX ISR", epr);
+                       if (ao_usb_epr_ctr_tx(epr)) {
+                               ao_usb_in_pending = 0;
+                               ao_wakeup(&ao_usb_in_pending);
+                       }
+                       break;
+               case AO_USB_INT_EPR:
+                       ++int_count;
+                       if (ao_usb_epr_ctr_tx(epr))
+                               _ao_usb_set_stat_tx(AO_USB_INT_EPR, STM_USB_EPR_STAT_TX_NAK);
+                       break;
+               }
+               return;
+       }
+
+       if (istr & (1 << STM_USB_ISTR_RESET)) {
+               ++reset_count;
+               stm_usb.istr &= ~(1UL << STM_USB_ISTR_RESET);
+               ao_usb_ep0_receive |= AO_USB_EP0_GOT_RESET;
+               ao_usb_ep0_handle(ao_usb_ep0_receive);
+       }
+}
+
+void
+stm_usb_wakeup_isr(void)
+{
+       /* USB wakeup, just clear the bit for now */
+       stm_usb.istr &= ~(1UL << STM_USB_ISTR_WKUP);
+}
+
+/* Queue the current IN buffer for transmission */
+static void
+_ao_usb_in_send(void)
+{
+       _tx_dbg0("in_send start");
+       debug ("send %d\n", ao_usb_tx_count);
+       while (ao_usb_in_pending)
+               ao_sleep(&ao_usb_in_pending);
+       ao_usb_in_pending = 1;
+       if (ao_usb_tx_count != AO_USB_IN_SIZE)
+               ao_usb_in_flushed = 1;
+       ao_usb_write(ao_usb_tx_buffer, ao_usb_in_tx_buffer, ao_usb_tx_count);
+       ao_usb_bdt[AO_USB_IN_EPR].single.count_tx = ao_usb_tx_count;
+       ao_usb_tx_count = 0;
+       _ao_usb_set_stat_tx(AO_USB_IN_EPR, STM_USB_EPR_STAT_TX_VALID);
+       _tx_dbg0("in_send end");
+}
+
+/* Wait for a free IN buffer. Interrupts are blocked */
+static void
+_ao_usb_in_wait(void)
+{
+       for (;;) {
+               /* Check if the current buffer is writable */
+               if (ao_usb_tx_count < AO_USB_IN_SIZE)
+                       break;
+
+               _tx_dbg0("in_wait top");
+               /* Wait for an IN buffer to be ready */
+               while (ao_usb_in_pending)
+                       ao_sleep(&ao_usb_in_pending);
+               _tx_dbg0("in_wait bottom");
+       }
+}
+
+void
+ao_usb_flush(void)
+{
+       if (!ao_usb_running)
+               return;
+
+       /* Anytime we've sent a character since
+        * the last time we flushed, we'll need
+        * to send a packet -- the only other time
+        * we would send a packet is when that
+        * packet was full, in which case we now
+        * want to send an empty packet
+        */
+       ao_arch_block_interrupts();
+       while (!ao_usb_in_flushed) {
+               _tx_dbg0("flush top");
+               _ao_usb_in_send();
+               _tx_dbg0("flush end");
+       }
+       ao_arch_release_interrupts();
+}
+
+void
+ao_usb_putchar(char c)
+{
+       if (!ao_usb_running)
+               return;
+
+       ao_arch_block_interrupts();
+       _ao_usb_in_wait();
+
+       ao_usb_in_flushed = 0;
+       ao_usb_tx_buffer[ao_usb_tx_count++] = (uint8_t) c;
+
+       /* Send the packet when full */
+       if (ao_usb_tx_count == AO_USB_IN_SIZE) {
+               _tx_dbg0("putchar full");
+               _ao_usb_in_send();
+               _tx_dbg0("putchar flushed");
+       }
+       ao_arch_release_interrupts();
+}
+
+static void
+_ao_usb_out_recv(void)
+{
+       _rx_dbg0("out_recv top");
+       ao_usb_out_avail = 0;
+
+       ao_usb_rx_count = (uint8_t) (ao_usb_bdt[AO_USB_OUT_EPR].single.count_rx & STM_USB_BDT_COUNT_RX_COUNT_RX_MASK);
+
+       _rx_dbg1("out_recv count", ao_usb_rx_count);
+       debug ("recv %d\n", ao_usb_rx_count);
+       debug_data("Fill OUT len %d:", ao_usb_rx_count);
+       ao_usb_read(ao_usb_rx_buffer, ao_usb_out_rx_buffer, 0, ao_usb_rx_count);
+       debug_data("\n");
+       ao_usb_rx_pos = 0;
+
+       /* ACK the packet */
+       _ao_usb_set_stat_rx(AO_USB_OUT_EPR, STM_USB_EPR_STAT_RX_VALID);
+}
+
+static int
+_ao_usb_pollchar(void)
+{
+       uint8_t c;
+
+       if (!ao_usb_running)
+               return AO_READ_AGAIN;
+
+       for (;;) {
+               if (ao_usb_rx_pos != ao_usb_rx_count)
+                       break;
+
+               _rx_dbg0("poll check");
+               /* Check to see if a packet has arrived */
+               if (!ao_usb_out_avail) {
+                       _rx_dbg0("poll none");
+                       return AO_READ_AGAIN;
+               }
+               _ao_usb_out_recv();
+       }
+
+       /* Pull a character out of the fifo */
+       c = ao_usb_rx_buffer[ao_usb_rx_pos++];
+       return c;
+}
+
+char
+ao_usb_getchar(void)
+{
+       int     c;
+
+       ao_arch_block_interrupts();
+       while ((c = _ao_usb_pollchar()) == AO_READ_AGAIN)
+               ao_sleep(AO_USB_OUT_SLEEP_ADDR);
+       ao_arch_release_interrupts();
+       return (char) c;
+}
+
+#ifndef HAS_USB_DISABLE
+#define HAS_USB_DISABLE 1
+#endif
+
+#if HAS_USB_DISABLE
+void
+ao_usb_disable(void)
+{
+       ao_arch_block_interrupts();
+       stm_usb.cntr = (1 << STM_USB_CNTR_FRES);
+       stm_usb.istr = 0;
+
+#if HAS_USB_PULLUP
+       /* Disable USB pull-up */
+       ao_gpio_set(AO_USB_PULLUP_PORT, AO_USB_PULLUP_PIN, 0);
+#endif
+
+       /* Switch off the device */
+       stm_usb.cntr = (1 << STM_USB_CNTR_PDWN) | (1 << STM_USB_CNTR_FRES);
+
+       /* Disable the interface */
+       stm_rcc.apb1enr &= ~(1UL << STM_RCC_APB1ENR_USBEN);
+       ao_arch_release_interrupts();
+}
+#endif
+
+void
+ao_usb_enable(void)
+{
+       int     t;
+
+#if HAS_USB_PULLUP
+       ao_gpio_set(AO_USB_PULLUP_PORT, AO_USB_PULLUP_PIN, 0);
+#endif
+
+       /* Enable USB device */
+       stm_rcc.apb1enr |= (1 << STM_RCC_APB1ENR_USBEN);
+
+       /* Do not touch the GPIOA configuration; USB takes priority
+        * over GPIO on pins A11 and A12, but if you select alternate
+        * input 10 (the documented correct selection), then USB is
+        * pulled low and doesn't work at all
+        */
+
+       ao_arch_block_interrupts();
+
+       /* Route interrupts */
+       stm_nvic_set_priority(STM_ISR_USB_LP_POS, AO_STM_NVIC_LOW_PRIORITY);
+       stm_nvic_set_enable(STM_ISR_USB_LP_POS);
+
+       ao_usb_configuration = 0;
+
+       stm_usb.cntr = (1 << STM_USB_CNTR_FRES);
+
+       /* Clear the power down bit */
+       stm_usb.cntr = 0;
+
+       /* Clear any spurious interrupts */
+       stm_usb.istr = 0;
+
+       debug ("ao_usb_enable\n");
+
+       /* Enable interrupts */
+       stm_usb.cntr = ((1 << STM_USB_CNTR_CTRM) |
+                       (0 << STM_USB_CNTR_PMAOVRM) |
+                       (0 << STM_USB_CNTR_ERRM) |
+                       (0 << STM_USB_CNTR_WKUPM) |
+                       (0 << STM_USB_CNTR_SUSPM) |
+                       (1 << STM_USB_CNTR_RESETM) |
+                       (0 << STM_USB_CNTR_SOFM) |
+                       (0 << STM_USB_CNTR_ESOFM) |
+                       (0 << STM_USB_CNTR_RESUME) |
+                       (0 << STM_USB_CNTR_FSUSP) |
+                       (0 << STM_USB_CNTR_LP_MODE) |
+                       (0 << STM_USB_CNTR_PDWN) |
+                       (0 << STM_USB_CNTR_FRES));
+
+       ao_arch_release_interrupts();
+
+       for (t = 0; t < 1000; t++)
+               ao_arch_nop();
+
+       /* Enable USB pull-up */
+#if HAS_USB_PULLUP
+       ao_gpio_set(AO_USB_PULLUP_PORT, AO_USB_PULLUP_PIN, 1);
+#endif
+}
+
+#if USB_ECHO
+struct ao_task ao_usb_echo_task;
+
+static void
+ao_usb_echo(void)
+{
+       char    c;
+
+       for (;;) {
+               c = ao_usb_getchar();
+               ao_usb_putchar(c);
+               ao_usb_flush();
+       }
+}
+#endif
+
+#if USB_DEBUG
+static void
+ao_usb_irq(void)
+{
+       printf ("control: %d out: %d in: %d int: %d reset: %d\n",
+               control_count, out_count, in_count, int_count, reset_count);
+}
+
+const struct ao_cmds ao_usb_cmds[] = {
+       { ao_usb_irq, "I\0Show USB interrupt counts" },
+       { 0, NULL }
+};
+#endif
+
+void
+ao_usb_init(void)
+{
+#if HAS_USB_PULLUP
+       int     i;
+       ao_enable_output(AO_USB_PULLUP_PORT, AO_USB_PULLUP_PIN, 0);
+       for (i = 0; i < 40000; i++)
+               ao_arch_nop();
+#endif
+       ao_usb_enable();
+
+       debug ("ao_usb_init\n");
+       ao_usb_ep0_state = AO_USB_EP0_IDLE;
+#if USB_ECHO
+       ao_add_task(&ao_usb_echo_task, ao_usb_echo, "usb echo");
+#endif
+#if USB_DEBUG
+       ao_cmd_register(&ao_usb_cmds[0]);
+#endif
+#if !USB_ECHO
+#if USE_USB_STDIO
+       ao_add_stdio(_ao_usb_pollchar, ao_usb_putchar, ao_usb_flush);
+#endif
+#endif
+}
+
+#if TX_DBG || RX_DBG
+
+struct ao_usb_dbg {
+       int             line;
+       char            *msg;
+       uint32_t        value;
+       uint32_t        prival;
+#if TX_DBG
+       uint16_t        in_count;
+       uint32_t        in_epr;
+       uint32_t        in_pending;
+       uint32_t        tx_count;
+       uint32_t        in_flushed;
+#endif
+#if RX_DBG
+       uint8_t         rx_count;
+       uint8_t         rx_pos;
+       uint8_t         out_avail;
+       uint32_t        out_epr;
+#endif
+};
+
+#define NUM_USB_DBG    16
+
+static struct ao_usb_dbg dbg[NUM_USB_DBG];
+static int dbg_i;
+
+static void _dbg(int line, char *msg, uint32_t value)
+{
+       uint32_t        prival;
+       dbg[dbg_i].line = line;
+       dbg[dbg_i].msg = msg;
+       dbg[dbg_i].value = value;
+#if AO_NONMASK_INTERRUPT
+       asm("mrs %0,basepri" : "=&r" (prival));
+#else
+       asm("mrs %0,primask" : "=&r" (prival));
+#endif
+       dbg[dbg_i].prival = prival;
+#if TX_DBG
+       dbg[dbg_i].in_count = in_count;
+       dbg[dbg_i].in_epr = stm_usb.epr[AO_USB_IN_EPR];
+       dbg[dbg_i].in_pending = ao_usb_in_pending;
+       dbg[dbg_i].tx_count = ao_usb_tx_count;
+       dbg[dbg_i].in_flushed = ao_usb_in_flushed;
+#endif
+#if RX_DBG
+       dbg[dbg_i].rx_count = ao_usb_rx_count;
+       dbg[dbg_i].rx_pos = ao_usb_rx_pos;
+       dbg[dbg_i].out_avail = ao_usb_out_avail;
+       dbg[dbg_i].out_epr = stm_usb.epr[AO_USB_OUT_EPR];
+#endif
+       if (++dbg_i == NUM_USB_DBG)
+               dbg_i = 0;
+}
+#endif