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dev_lowlevel
for Raspberry Pi Picoโ„ข W, submitted by flashmypico

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/**
* Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <stdio.h>
// Pico
#include "pico/stdlib.h"
// For memcpy
#include <string.h>
// Include descriptor struct definitions
#include "usb_common.h"
// USB register definitions from pico-sdk
#include "hardware/regs/usb.h"
// USB hardware struct definitions from pico-sdk
#include "hardware/structs/usb.h"
// For interrupt enable and numbers
#include "hardware/irq.h"
// For resetting the USB controller
#include "hardware/resets.h"
// Device descriptors
#include "dev_lowlevel.h"
#define usb_hw_set ((usb_hw_t *)hw_set_alias_untyped(usb_hw))
#define usb_hw_clear ((usb_hw_t *)hw_clear_alias_untyped(usb_hw))
// Function prototypes for our device specific endpoint handlers defined
// later on
void ep0_in_handler(uint8_t *buf, uint16_t len);
void ep0_out_handler(uint8_t *buf, uint16_t len);
void ep1_out_handler(uint8_t *buf, uint16_t len);
void ep2_in_handler(uint8_t *buf, uint16_t len);
// Global device address
static bool should_set_address = false;
static uint8_t dev_addr = 0;
static volatile bool configured = false;
// Global data buffer for EP0
static uint8_t ep0_buf[64];
// Struct defining the device configuration
static struct usb_device_configuration dev_config = {
.device_descriptor = &device_descriptor,
.interface_descriptor = &interface_descriptor,
.config_descriptor = &config_descriptor,
.lang_descriptor = lang_descriptor,
.descriptor_strings = descriptor_strings,
.endpoints = {
{
.descriptor = &ep0_out,
.handler = &ep0_out_handler,
.endpoint_control = NULL, // NA for EP0
.buffer_control = &usb_dpram->ep_buf_ctrl[0].out,
// EP0 in and out share a data buffer
.data_buffer = &usb_dpram->ep0_buf_a[0],
},
{
.descriptor = &ep0_in,
.handler = &ep0_in_handler,
.endpoint_control = NULL, // NA for EP0,
.buffer_control = &usb_dpram->ep_buf_ctrl[0].in,
// EP0 in and out share a data buffer
.data_buffer = &usb_dpram->ep0_buf_a[0],
},
{
.descriptor = &ep1_out,
.handler = &ep1_out_handler,
// EP1 starts at offset 0 for endpoint control
.endpoint_control = &usb_dpram->ep_ctrl[0].out,
.buffer_control = &usb_dpram->ep_buf_ctrl[1].out,
// First free EPX buffer
.data_buffer = &usb_dpram->epx_data[0 * 64],
},
{
.descriptor = &ep2_in,
.handler = &ep2_in_handler,
.endpoint_control = &usb_dpram->ep_ctrl[1].in,
.buffer_control = &usb_dpram->ep_buf_ctrl[2].in,
// Second free EPX buffer
.data_buffer = &usb_dpram->epx_data[1 * 64],
}
}
};
/**
* @brief Given an endpoint address, return the usb_endpoint_configuration of that endpoint. Returns NULL
* if an endpoint of that address is not found.
*
* @param addr
* @return struct usb_endpoint_configuration*
*/
struct usb_endpoint_configuration *usb_get_endpoint_configuration(uint8_t addr) {
struct usb_endpoint_configuration *endpoints = dev_config.endpoints;
for (int i = 0; i < USB_NUM_ENDPOINTS; i++) {
if (endpoints[i].descriptor && (endpoints[i].descriptor->bEndpointAddress == addr)) {
return &endpoints[i];
}
}
return NULL;
}
/**
* @brief Given a C string, fill the EP0 data buf with a USB string descriptor for that string.
*
* @param C string you would like to send to the USB host
* @return the length of the string descriptor in EP0 buf
*/
uint8_t usb_prepare_string_descriptor(const unsigned char *str) {
// 2 for bLength + bDescriptorType + strlen * 2 because string is unicode. i.e. other byte will be 0
uint8_t bLength = 2 + (strlen((const char *)str) * 2);
static const uint8_t bDescriptorType = 0x03;
volatile uint8_t *buf = &ep0_buf[0];
*buf++ = bLength;
*buf++ = bDescriptorType;
uint8_t c;
do {
c = *str++;
*buf++ = c;
*buf++ = 0;
} while (c != '\0');
return bLength;
}
/**
* @brief Take a buffer pointer located in the USB RAM and return as an offset of the RAM.
*
* @param buf
* @return uint32_t
*/
static inline uint32_t usb_buffer_offset(volatile uint8_t *buf) {
return (uint32_t) buf ^ (uint32_t) usb_dpram;
}
/**
* @brief Set up the endpoint control register for an endpoint (if applicable. Not valid for EP0).
*
* @param ep
*/
void usb_setup_endpoint(const struct usb_endpoint_configuration *ep) {
printf("Set up endpoint 0x%x with buffer address 0x%p\n", ep->descriptor->bEndpointAddress, ep->data_buffer);
// EP0 doesn't have one so return if that is the case
if (!ep->endpoint_control) {
return;
}
// Get the data buffer as an offset of the USB controller's DPRAM
uint32_t dpram_offset = usb_buffer_offset(ep->data_buffer);
uint32_t reg = EP_CTRL_ENABLE_BITS
| EP_CTRL_INTERRUPT_PER_BUFFER
| (ep->descriptor->bmAttributes << EP_CTRL_BUFFER_TYPE_LSB)
| dpram_offset;
*ep->endpoint_control = reg;
}
/**
* @brief Set up the endpoint control register for each endpoint.
*
*/
void usb_setup_endpoints() {
const struct usb_endpoint_configuration *endpoints = dev_config.endpoints;
for (int i = 0; i < USB_NUM_ENDPOINTS; i++) {
if (endpoints[i].descriptor && endpoints[i].handler) {
usb_setup_endpoint(&endpoints[i]);
}
}
}
/**
* @brief Set up the USB controller in device mode, clearing any previous state.
*
*/
void usb_device_init() {
// Reset usb controller
reset_unreset_block_num_wait_blocking(RESET_USBCTRL);
// Clear any previous state in dpram just in case
memset(usb_dpram, 0, sizeof(*usb_dpram)); // <1>
// Enable USB interrupt at processor
irq_set_enabled(USBCTRL_IRQ, true);
// Mux the controller to the onboard usb phy
usb_hw->muxing = USB_USB_MUXING_TO_PHY_BITS | USB_USB_MUXING_SOFTCON_BITS;
// Force VBUS detect so the device thinks it is plugged into a host
usb_hw->pwr = USB_USB_PWR_VBUS_DETECT_BITS | USB_USB_PWR_VBUS_DETECT_OVERRIDE_EN_BITS;
// Enable the USB controller in device mode.
usb_hw->main_ctrl = USB_MAIN_CTRL_CONTROLLER_EN_BITS;
// Enable an interrupt per EP0 transaction
usb_hw->sie_ctrl = USB_SIE_CTRL_EP0_INT_1BUF_BITS; // <2>
// Enable interrupts for when a buffer is done, when the bus is reset,
// and when a setup packet is received
usb_hw->inte = USB_INTS_BUFF_STATUS_BITS |
USB_INTS_BUS_RESET_BITS |
USB_INTS_SETUP_REQ_BITS;
// Set up endpoints (endpoint control registers)
// described by device configuration
usb_setup_endpoints();
// Present full speed device by enabling pull up on DP
usb_hw_set->sie_ctrl = USB_SIE_CTRL_PULLUP_EN_BITS;
}
/**
* @brief Given an endpoint configuration, returns true if the endpoint
* is transmitting data to the host (i.e. is an IN endpoint)
*
* @param ep, the endpoint configuration
* @return true
* @return false
*/
static inline bool ep_is_tx(struct usb_endpoint_configuration *ep) {
return ep->descriptor->bEndpointAddress & USB_DIR_IN;
}
/**
* @brief Starts a transfer on a given endpoint.
*
* @param ep, the endpoint configuration.
* @param buf, the data buffer to send. Only applicable if the endpoint is TX
* @param len, the length of the data in buf (this example limits max len to one packet - 64 bytes)
*/
void usb_start_transfer(struct usb_endpoint_configuration *ep, uint8_t *buf, uint16_t len) {
// We are asserting that the length is <= 64 bytes for simplicity of the example.
// For multi packet transfers see the tinyusb port.
assert(len <= 64);
printf("Start transfer of len %d on ep addr 0x%x\n", len, ep->descriptor->bEndpointAddress);
// Prepare buffer control register value
uint32_t val = len | USB_BUF_CTRL_AVAIL;
if (ep_is_tx(ep)) {
// Need to copy the data from the user buffer to the usb memory
memcpy((void *) ep->data_buffer, (void *) buf, len);
// Mark as full
val |= USB_BUF_CTRL_FULL;
}
// Set pid and flip for next transfer
val |= ep->next_pid ? USB_BUF_CTRL_DATA1_PID : USB_BUF_CTRL_DATA0_PID;
ep->next_pid ^= 1u;
*ep->buffer_control = val;
}
/**
* @brief Send device descriptor to host
*
*/
void usb_handle_device_descriptor(volatile struct usb_setup_packet *pkt) {
const struct usb_device_descriptor *d = dev_config.device_descriptor;
// EP0 in
struct usb_endpoint_configuration *ep = usb_get_endpoint_configuration(EP0_IN_ADDR);
// Always respond with pid 1
ep->next_pid = 1;
usb_start_transfer(ep, (uint8_t *) d, MIN(sizeof(struct usb_device_descriptor), pkt->wLength));
}
/**
* @brief Send the configuration descriptor (and potentially the configuration and endpoint descriptors) to the host.
*
* @param pkt, the setup packet received from the host.
*/
void usb_handle_config_descriptor(volatile struct usb_setup_packet *pkt) {
uint8_t *buf = &ep0_buf[0];
// First request will want just the config descriptor
const struct usb_configuration_descriptor *d = dev_config.config_descriptor;
memcpy((void *) buf, d, sizeof(struct usb_configuration_descriptor));
buf += sizeof(struct usb_configuration_descriptor);
// If we more than just the config descriptor copy it all
if (pkt->wLength >= d->wTotalLength) {
memcpy((void *) buf, dev_config.interface_descriptor, sizeof(struct usb_interface_descriptor));
buf += sizeof(struct usb_interface_descriptor);
const struct usb_endpoint_configuration *ep = dev_config.endpoints;
// Copy all the endpoint descriptors starting from EP1
for (uint i = 2; i < USB_NUM_ENDPOINTS; i++) {
if (ep[i].descriptor) {
memcpy((void *) buf, ep[i].descriptor, sizeof(struct usb_endpoint_descriptor));
buf += sizeof(struct usb_endpoint_descriptor);
}
}
}
// Send data
// Get len by working out end of buffer subtract start of buffer
uint32_t len = (uint32_t) buf - (uint32_t) &ep0_buf[0];
usb_start_transfer(usb_get_endpoint_configuration(EP0_IN_ADDR), &ep0_buf[0], MIN(len, pkt->wLength));
}
/**
* @brief Handle a BUS RESET from the host by setting the device address back to 0.
*
*/
void usb_bus_reset(void) {
// Set address back to 0
dev_addr = 0;
should_set_address = false;
usb_hw->dev_addr_ctrl = 0;
configured = false;
}
/**
* @brief Send the requested string descriptor to the host.
*
* @param pkt, the setup packet from the host.
*/
void usb_handle_string_descriptor(volatile struct usb_setup_packet *pkt) {
uint8_t i = pkt->wValue & 0xff;
uint8_t len = 0;
if (i == 0) {
len = 4;
memcpy(&ep0_buf[0], dev_config.lang_descriptor, len);
} else {
// Prepare fills in ep0_buf
len = usb_prepare_string_descriptor(dev_config.descriptor_strings[i - 1]);
}
usb_start_transfer(usb_get_endpoint_configuration(EP0_IN_ADDR), &ep0_buf[0], MIN(len, pkt->wLength));
}
/**
* @brief Sends a zero length status packet back to the host.
*/
void usb_acknowledge_out_request(void) {
usb_start_transfer(usb_get_endpoint_configuration(EP0_IN_ADDR), NULL, 0);
}
/**
* @brief Handles a SET_ADDR request from the host. The actual setting of the device address in
* hardware is done in ep0_in_handler. This is because we have to acknowledge the request first
* as a device with address zero.
*
* @param pkt, the setup packet from the host.
*/
void usb_set_device_address(volatile struct usb_setup_packet *pkt) {
// Set address is a bit of a strange case because we have to send a 0 length status packet first with
// address 0
dev_addr = (pkt->wValue & 0xff);
printf("Set address %d\r\n", dev_addr);
// Will set address in the callback phase
should_set_address = true;
usb_acknowledge_out_request();
}
/**
* @brief Handles a SET_CONFIGRUATION request from the host. Assumes one configuration so simply
* sends a zero length status packet back to the host.
*
* @param pkt, the setup packet from the host.
*/
void usb_set_device_configuration(__unused volatile struct usb_setup_packet *pkt) {
// Only one configuration so just acknowledge the request
printf("Device Enumerated\r\n");
usb_acknowledge_out_request();
configured = true;
}
/**
* @brief Respond to a setup packet from the host.
*
*/
void usb_handle_setup_packet(void) {
volatile struct usb_setup_packet *pkt = (volatile struct usb_setup_packet *) &usb_dpram->setup_packet;
uint8_t req_direction = pkt->bmRequestType;
uint8_t req = pkt->bRequest;
// Reset PID to 1 for EP0 IN
usb_get_endpoint_configuration(EP0_IN_ADDR)->next_pid = 1u;
if (req_direction == USB_DIR_OUT) {
if (req == USB_REQUEST_SET_ADDRESS) {
usb_set_device_address(pkt);
} else if (req == USB_REQUEST_SET_CONFIGURATION) {
usb_set_device_configuration(pkt);
} else {
usb_acknowledge_out_request();
printf("Other OUT request (0x%x)\r\n", pkt->bRequest);
}
} else if (req_direction == USB_DIR_IN) {
if (req == USB_REQUEST_GET_DESCRIPTOR) {
uint16_t descriptor_type = pkt->wValue >> 8;
switch (descriptor_type) {
case USB_DT_DEVICE:
usb_handle_device_descriptor(pkt);
printf("GET DEVICE DESCRIPTOR\r\n");
break;
case USB_DT_CONFIG:
usb_handle_config_descriptor(pkt);
printf("GET CONFIG DESCRIPTOR\r\n");
break;
case USB_DT_STRING:
usb_handle_string_descriptor(pkt);
printf("GET STRING DESCRIPTOR\r\n");
break;
default:
printf("Unhandled GET_DESCRIPTOR type 0x%x\r\n", descriptor_type);
}
} else {
printf("Other IN request (0x%x)\r\n", pkt->bRequest);
}
}
}
/**
* @brief Notify an endpoint that a transfer has completed.
*
* @param ep, the endpoint to notify.
*/
static void usb_handle_ep_buff_done(struct usb_endpoint_configuration *ep) {
uint32_t buffer_control = *ep->buffer_control;
// Get the transfer length for this endpoint
uint16_t len = buffer_control & USB_BUF_CTRL_LEN_MASK;
// Call that endpoints buffer done handler
ep->handler((uint8_t *) ep->data_buffer, len);
}
/**
* @brief Find the endpoint configuration for a specified endpoint number and
* direction and notify it that a transfer has completed.
*
* @param ep_num
* @param in
*/
static void usb_handle_buff_done(uint ep_num, bool in) {
uint8_t ep_addr = ep_num | (in ? USB_DIR_IN : 0);
printf("EP %d (in = %d) done\n", ep_num, in);
for (uint i = 0; i < USB_NUM_ENDPOINTS; i++) {
struct usb_endpoint_configuration *ep = &dev_config.endpoints[i];
if (ep->descriptor && ep->handler) {
if (ep->descriptor->bEndpointAddress == ep_addr) {
usb_handle_ep_buff_done(ep);
return;
}
}
}
}
/**
* @brief Handle a "buffer status" irq. This means that one or more
* buffers have been sent / received. Notify each endpoint where this
* is the case.
*/
static void usb_handle_buff_status() {
uint32_t buffers = usb_hw->buf_status;
uint32_t remaining_buffers = buffers;
uint bit = 1u;
for (uint i = 0; remaining_buffers && i < USB_NUM_ENDPOINTS * 2; i++) {
if (remaining_buffers & bit) {
// clear this in advance
usb_hw_clear->buf_status = bit;
// IN transfer for even i, OUT transfer for odd i
usb_handle_buff_done(i >> 1u, !(i & 1u));
remaining_buffers &= ~bit;
}
bit <<= 1u;
}
}
/**
* @brief USB interrupt handler
*
*/
#ifdef __cplusplus
extern "C" {
#endif
/// \tag::isr_setup_packet[]
void isr_usbctrl(void) {
// USB interrupt handler
uint32_t status = usb_hw->ints;
uint32_t handled = 0;
// Setup packet received
if (status & USB_INTS_SETUP_REQ_BITS) {
handled |= USB_INTS_SETUP_REQ_BITS;
usb_hw_clear->sie_status = USB_SIE_STATUS_SETUP_REC_BITS;
usb_handle_setup_packet();
}
/// \end::isr_setup_packet[]
// Buffer status, one or more buffers have completed
if (status & USB_INTS_BUFF_STATUS_BITS) {
handled |= USB_INTS_BUFF_STATUS_BITS;
usb_handle_buff_status();
}
// Bus is reset
if (status & USB_INTS_BUS_RESET_BITS) {
printf("BUS RESET\n");
handled |= USB_INTS_BUS_RESET_BITS;
usb_hw_clear->sie_status = USB_SIE_STATUS_BUS_RESET_BITS;
usb_bus_reset();
}
if (status ^ handled) {
panic("Unhandled IRQ 0x%x\n", (uint) (status ^ handled));
}
}
#ifdef __cplusplus
}
#endif
/**
* @brief EP0 in transfer complete. Either finish the SET_ADDRESS process, or receive a zero
* length status packet from the host.
*
* @param buf the data that was sent
* @param len the length that was sent
*/
void ep0_in_handler(__unused uint8_t *buf, __unused uint16_t len) {
if (should_set_address) {
// Set actual device address in hardware
usb_hw->dev_addr_ctrl = dev_addr;
should_set_address = false;
} else {
// Receive a zero length status packet from the host on EP0 OUT
struct usb_endpoint_configuration *ep = usb_get_endpoint_configuration(EP0_OUT_ADDR);
usb_start_transfer(ep, NULL, 0);
}
}
void ep0_out_handler(__unused uint8_t *buf, __unused uint16_t len) {
}
// Device specific functions
void ep1_out_handler(uint8_t *buf, uint16_t len) {
printf("RX %d bytes from host\n", len);
// Send data back to host
struct usb_endpoint_configuration *ep = usb_get_endpoint_configuration(EP2_IN_ADDR);
usb_start_transfer(ep, buf, len);
}
void ep2_in_handler(__unused uint8_t *buf, uint16_t len) {
printf("Sent %d bytes to host\n", len);
// Get ready to rx again from host
usb_start_transfer(usb_get_endpoint_configuration(EP1_OUT_ADDR), NULL, 64);
}
int main(void) {
stdio_init_all();
printf("USB Device Low-Level hardware example\n");
usb_device_init();
// Wait until configured
while (!configured) {
tight_loop_contents();
}
// Get ready to rx from host
usb_start_transfer(usb_get_endpoint_configuration(EP1_OUT_ADDR), NULL, 64);
// Everything is interrupt driven so just loop here
while (1) {
tight_loop_contents();
}
}
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This firmware image was imported from the pico-examples repository. 


Copyright 2020 (c) 2020 Raspberry Pi (Trading) Ltd.

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   disclaimer.

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   disclaimer in the documentation and/or other materials provided with the distribution.

3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products
   derived from this software without specific prior written permission.

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INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Homepage: https://github.com/raspberrypi/pico-examples
Repository: https://github.com/raspberrypi/pico-examples/tree/master/usb/device/dev_lowlevel

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