USB Serial Speed compared to UART Serial Driver Speed
Posted: Tue May 20, 2014 1:52 pm
Hi guys,
I am currently using chibios 2.6.3 and a STM32F4 Discovery with the STM32F407 chip.
And I have some trouble concerning the usb serial driver. It seems to be rather slow compared to an uart serial driver.
My task wakes up from an interrupt that happens each 10ms (frequency of 100Hz). As the task wakes up it toggles the green led and reads an register of the sensor (mpu9150) which drives the interrupt. This register represents the reason of the interrupt. If it was an overflow of its fifo, than the stm32f4 resets the fifo and enables it again. In the other case (sensor data is available) the stm32f4 tries to read how much data is available and reads this amount of datta from fifo of the sensor. After having done that the stm32f4 writes the amount of data that was read to the uart serial driver. Then the microcontoller checks wether the task was faster done than the interrupt frequency. So ideally there should be 14 bytes of that if all went right. There should be 14 bytes because this is the magic number of bytes which the sensor samples in one measurement.
And there is my problem: If I use the SDU1 instead of the SD3 (which is configured at 115200 baud), I get more than the 14 bytes in the Fifo. Therefore I miss some interrupts. To indicate this error the Orange and Red leds are going to light up.
And there is my code:
So my question is whether this behavior is normal? Is the USB Serial Driver really slower than the UART Serial driver? I didn't expect that.
I also have to note that I really do not have any glue how the USB Serial Driver works and how to configure it properly. I only got some example configuration and used that. So this is my usb configuration:
myUSB.c
usbdescriptor.h
Thanks for your help and kind regards,
Tobias
I am currently using chibios 2.6.3 and a STM32F4 Discovery with the STM32F407 chip.
And I have some trouble concerning the usb serial driver. It seems to be rather slow compared to an uart serial driver.
My task wakes up from an interrupt that happens each 10ms (frequency of 100Hz). As the task wakes up it toggles the green led and reads an register of the sensor (mpu9150) which drives the interrupt. This register represents the reason of the interrupt. If it was an overflow of its fifo, than the stm32f4 resets the fifo and enables it again. In the other case (sensor data is available) the stm32f4 tries to read how much data is available and reads this amount of datta from fifo of the sensor. After having done that the stm32f4 writes the amount of data that was read to the uart serial driver. Then the microcontoller checks wether the task was faster done than the interrupt frequency. So ideally there should be 14 bytes of that if all went right. There should be 14 bytes because this is the magic number of bytes which the sensor samples in one measurement.
And there is my problem: If I use the SDU1 instead of the SD3 (which is configured at 115200 baud), I get more than the 14 bytes in the Fifo. Therefore I miss some interrupts. To indicate this error the Orange and Red leds are going to light up.
And there is my code:
Code: Select all
class IntThread : public BaseStaticThread<2048> {
protected:
virtual msg_t main(void) {
uint8_t status;
uint8_t buffer[1030];
setName("IntThread");
while (TRUE) {
/* Checks if an IRQ happened else wait.*/
this->waitAnyEvent((eventmask_t)1);
/* Perform processing here.*/
palTogglePad(GPIOD, 12);
status = modules::sensors::mpu.getIntStatus();
if (status&(1<<4))
{
modules::sensors::mpu.resetFIFO();
//BaseThread::sleep(MS2ST(10));
modules::sensors::mpu.setFIFOEnabled(true);
}
else
{
uint16_t count = 0;
count = modules::sensors::mpu.getFIFOCount();
modules::sensors::mpu.getFIFOBytes(buffer, count);
chprintf(reinterpret_cast<BaseSequentialStream *>(&SD3), "Count: %u\n\r", count);
//chprintf(reinterpret_cast<BaseSequentialStream *>(&SDU1), "Count: %u\n\r", count);
if (count != 14)
{
palSetPad(GPIOD, 13);
palTogglePad(GPIOD, 14);
}
}
}
}
public:
IntThread(void) : BaseStaticThread<2048>() {
}
};
So my question is whether this behavior is normal? Is the USB Serial Driver really slower than the UART Serial driver? I didn't expect that.
I also have to note that I really do not have any glue how the USB Serial Driver works and how to configure it properly. I only got some example configuration and used that. So this is my usb configuration:
myUSB.c
Code: Select all
#include "ch.h"
#include "hal.h"
//#include "shell.h"
#include "myUSB.h"
#include "usbdescriptor.h"
/*
* Don't ask me, I have no idea what is done here...
* I think most things are either self explanatory, well documented or not to be touched
*/
/*
* USB Driver structure.
*/
SerialUSBDriver SDU1;
/*===========================================================================*/
/* USB related stuff. */
/*===========================================================================*/
/*
* Endpoints to be used for USBD1.
*/
#define USBD1_DATA_REQUEST_EP 1
#define USBD1_DATA_AVAILABLE_EP 1
#define USBD1_INTERRUPT_REQUEST_EP 2
/*
* Handles the GET_DESCRIPTOR callback. All required descriptors must be
* handled here.
*/
static const USBDescriptor *get_descriptor(USBDriver *usbp,
uint8_t dtype,
uint8_t dindex,
uint16_t lang) {
(void)usbp;
(void)lang;
switch (dtype) {
case USB_DESCRIPTOR_DEVICE:
return &vcom_device_descriptor;
case USB_DESCRIPTOR_CONFIGURATION:
return &vcom_configuration_descriptor;
case USB_DESCRIPTOR_STRING:
if (dindex < 4)
return &vcom_strings[dindex];
}
return NULL;
}
/**
* @brief IN EP1 state.
*/
static USBInEndpointState ep1instate;
/**
* @brief OUT EP1 state.
*/
static USBOutEndpointState ep1outstate;
/**
* @brief EP1 initialization structure (both IN and OUT).
*/
static const USBEndpointConfig ep1config = {
USB_EP_MODE_TYPE_BULK,
NULL,
sduDataTransmitted,
sduDataReceived,
0x0040,
0x0040,
&ep1instate,
&ep1outstate,
2,
NULL
};
/**
* @brief IN EP2 state.
*/
static USBInEndpointState ep2instate;
/**
* @brief EP2 initialization structure (IN only).
*/
static const USBEndpointConfig ep2config = {
USB_EP_MODE_TYPE_INTR,
NULL,
sduInterruptTransmitted,
NULL,
0x0010,
0x0000,
&ep2instate,
NULL,
1,
NULL
};
/*
* Handles the USB driver global events.
*/
static void usb_event(USBDriver *usbp, usbevent_t event) {
extern SerialUSBDriver SDU1;
switch (event) {
case USB_EVENT_RESET:
return;
case USB_EVENT_ADDRESS:
return;
case USB_EVENT_CONFIGURED:
chSysLockFromIsr();
/* Enables the endpoints specified into the configuration.
Note, this callback is invoked from an ISR so I-Class functions
must be used.*/
usbInitEndpointI(usbp, USBD1_DATA_REQUEST_EP, &ep1config);
usbInitEndpointI(usbp, USBD1_INTERRUPT_REQUEST_EP, &ep2config);
/* Resetting the state of the CDC subsystem.*/
sduConfigureHookI(&SDU1);
chSysUnlockFromIsr();
return;
case USB_EVENT_SUSPEND:
return;
case USB_EVENT_WAKEUP:
return;
case USB_EVENT_STALLED:
return;
}
return;
}
/*
* USB driver configuration.
*/
const USBConfig usbcfg = {
usb_event,
get_descriptor,
sduRequestsHook,
NULL
};
/*
* Serial over USB driver configuration.
*/
const SerialUSBConfig serusbcfg = {
&USBD1,
USBD1_DATA_REQUEST_EP,
USBD1_DATA_AVAILABLE_EP,
USBD1_INTERRUPT_REQUEST_EP
};
int isUsbActive(void){
return SDU1.config->usbp->state == USB_ACTIVE;
}
void myUSBinit(void){
/*
* Shell manager initialization.
*/
//shellInit();
/*
* Initializes a serial-over-USB CDC driver.
*/
sduObjectInit(&SDU1);
sduStart(&SDU1, &serusbcfg);
/*
* Activates the USB driver and then the USB bus pull-up on D+.
* Note, a delay is inserted in order to not have to disconnect the cable
* after a reset.
*/
usbDisconnectBus(serusbcfg.usbp);
chThdSleepMilliseconds(1000);
usbStart(serusbcfg.usbp, &usbcfg);
//chThdSleepMilliseconds(1000);
usbConnectBus(serusbcfg.usbp);
//chThdSleepMilliseconds(1000);
}usbdescriptor.h
Code: Select all
#ifndef USBDESCRIPTOR_H_INCLUDED
#define USBDESCRIPTOR_H_INCLUDED
/*
* Endpoints to be used for USBD1.
*/
#define USBD1_DATA_REQUEST_EP 1
#define USBD1_DATA_AVAILABLE_EP 1
#define USBD1_INTERRUPT_REQUEST_EP 2
/*
* USB Device Descriptor.
*/
static const uint8_t vcom_device_descriptor_data[18] = {
USB_DESC_DEVICE (0x0110, /* bcdUSB (1.1). */
0x02, /* bDeviceClass (CDC). */
0x00, /* bDeviceSubClass. */
0x00, /* bDeviceProtocol. */
0x40, /* bMaxPacketSize. */
0x0483, /* idVendor (ST). */
0x5740, /* idProduct. */
0x0200, /* bcdDevice. */
1, /* iManufacturer. */
2, /* iProduct. */
3, /* iSerialNumber. */
1) /* bNumConfigurations. */
};
/*
* Device Descriptor wrapper.
*/
static const USBDescriptor vcom_device_descriptor = {
sizeof vcom_device_descriptor_data,
vcom_device_descriptor_data
};
/* Configuration Descriptor tree for a CDC.*/
static const uint8_t vcom_configuration_descriptor_data[67] = {
/* Configuration Descriptor.*/
USB_DESC_CONFIGURATION(67, /* wTotalLength. */
0x02, /* bNumInterfaces. */
0x01, /* bConfigurationValue. */
0, /* iConfiguration. */
0xC0, /* bmAttributes (self powered). */
50), /* bMaxPower (100mA). */
/* Interface Descriptor.*/
USB_DESC_INTERFACE (0x00, /* bInterfaceNumber. */
0x00, /* bAlternateSetting. */
0x01, /* bNumEndpoints. */
0x02, /* bInterfaceClass (Communications
Interface Class, CDC section
4.2). */
0x02, /* bInterfaceSubClass (Abstract
Control Model, CDC section 4.3). */
0x01, /* bInterfaceProtocol (AT commands,
CDC section 4.4). */
0), /* iInterface. */
/* Header Functional Descriptor (CDC section 5.2.3).*/
USB_DESC_BYTE (5), /* bLength. */
USB_DESC_BYTE (0x24), /* bDescriptorType (CS_INTERFACE). */
USB_DESC_BYTE (0x00), /* bDescriptorSubtype (Header
Functional Descriptor. */
USB_DESC_BCD (0x0110), /* bcdCDC. */
/* Call Management Functional Descriptor. */
USB_DESC_BYTE (5), /* bFunctionLength. */
USB_DESC_BYTE (0x24), /* bDescriptorType (CS_INTERFACE). */
USB_DESC_BYTE (0x01), /* bDescriptorSubtype (Call Management
Functional Descriptor). */
USB_DESC_BYTE (0x00), /* bmCapabilities (D0+D1). */
USB_DESC_BYTE (0x01), /* bDataInterface. */
/* ACM Functional Descriptor.*/
USB_DESC_BYTE (4), /* bFunctionLength. */
USB_DESC_BYTE (0x24), /* bDescriptorType (CS_INTERFACE). */
USB_DESC_BYTE (0x02), /* bDescriptorSubtype (Abstract
Control Management Descriptor). */
USB_DESC_BYTE (0x02), /* bmCapabilities. */
/* Union Functional Descriptor.*/
USB_DESC_BYTE (5), /* bFunctionLength. */
USB_DESC_BYTE (0x24), /* bDescriptorType (CS_INTERFACE). */
USB_DESC_BYTE (0x06), /* bDescriptorSubtype (Union
Functional Descriptor). */
USB_DESC_BYTE (0x00), /* bMasterInterface (Communication
Class Interface). */
USB_DESC_BYTE (0x01), /* bSlaveInterface0 (Data Class
Interface). */
/* Endpoint 2 Descriptor.*/
USB_DESC_ENDPOINT (USBD1_INTERRUPT_REQUEST_EP|0x80,
0x03, /* bmAttributes (Interrupt). */
0x0008, /* wMaxPacketSize. */
0xFF), /* bInterval. */
/* Interface Descriptor.*/
USB_DESC_INTERFACE (0x01, /* bInterfaceNumber. */
0x00, /* bAlternateSetting. */
0x02, /* bNumEndpoints. */
0x0A, /* bInterfaceClass (Data Class
Interface, CDC section 4.5). */
0x00, /* bInterfaceSubClass (CDC section
4.6). */
0x00, /* bInterfaceProtocol (CDC section
4.7). */
0x00), /* iInterface. */
/* Endpoint 3 Descriptor.*/
USB_DESC_ENDPOINT (USBD1_DATA_AVAILABLE_EP, /* bEndpointAddress.*/
0x02, /* bmAttributes (Bulk). */
0x0040, /* wMaxPacketSize. */
0x00), /* bInterval. */
/* Endpoint 1 Descriptor.*/
USB_DESC_ENDPOINT (USBD1_DATA_REQUEST_EP|0x80, /* bEndpointAddress.*/
0x02, /* bmAttributes (Bulk). */
0x0040, /* wMaxPacketSize. */
0x00) /* bInterval. */
};
/*
* Configuration Descriptor wrapper.
*/
static const USBDescriptor vcom_configuration_descriptor = {
sizeof vcom_configuration_descriptor_data,
vcom_configuration_descriptor_data
};
/*
* U.S. English language identifier.
*/
static const uint8_t vcom_string0[] = {
USB_DESC_BYTE(4), /* bLength. */
USB_DESC_BYTE(USB_DESCRIPTOR_STRING), /* bDescriptorType. */
USB_DESC_WORD(0x0409) /* wLANGID (U.S. English). */
};
/*
* Vendor string.
*/
static const uint8_t vcom_string1[] = {
USB_DESC_BYTE(38), /* bLength. */
USB_DESC_BYTE(USB_DESCRIPTOR_STRING), /* bDescriptorType. */
'S', 0, 'T', 0, 'M', 0, 'i', 0, 'c', 0, 'r', 0, 'o', 0, 'e', 0,
'l', 0, 'e', 0, 'c', 0, 't', 0, 'r', 0, 'o', 0, 'n', 0, 'i', 0,
'c', 0, 's', 0
};
/*
* Device Description string.
*/
static const uint8_t vcom_string2[] = {
USB_DESC_BYTE(56), /* bLength. */
USB_DESC_BYTE(USB_DESCRIPTOR_STRING), /* bDescriptorType. */
'C', 0, 'h', 0, 'i', 0, 'b', 0, 'i', 0, 'O', 0, 'S', 0, '/', 0,
'R', 0, 'T', 0, ' ', 0, 'V', 0, 'i', 0, 'r', 0, 't', 0, 'u', 0,
'a', 0, 'l', 0, ' ', 0, 'C', 0, 'O', 0, 'M', 0, ' ', 0, 'P', 0,
'o', 0, 'r', 0, 't', 0
};
/*
* Serial Number string.
*/
static const uint8_t vcom_string3[] = {
USB_DESC_BYTE(8), /* bLength. */
USB_DESC_BYTE(USB_DESCRIPTOR_STRING), /* bDescriptorType. */
'0' + CH_KERNEL_MAJOR, 0,
'0' + CH_KERNEL_MINOR, 0,
'0' + CH_KERNEL_PATCH, 0
};
/*
* Strings wrappers array.
*/
static const USBDescriptor vcom_strings[] = {
{sizeof vcom_string0, vcom_string0},
{sizeof vcom_string1, vcom_string1},
{sizeof vcom_string2, vcom_string2},
{sizeof vcom_string3, vcom_string3}
};
#endif // USBDESCRIPTOR_H_INCLUDEDThanks for your help and kind regards,
Tobias