Posted on August 23, 2016 at 17:29
Hi marco,
1) Testing on my side,
I tested this issue on my F4 discovery board with Cube,
- CubeMX: v4.0
- CubeF4: v1.0
A HID USB host was generated using CubeMX.
The STM32 host had successfully enumerated a low-speed mouse (with a minor fix **1)
On this setup, the keep-alive interval was measured on a hardware bus analyzer.
- 90 cycles of keep-alive were 35 micro-sec longer, relatively to the analyzer's internal clock.
that is, about 389 ns per cycle.
This figure satisfies the USB spec's tolerance (+/-500ns), but it seems slightly greater than expected, while they are running on crystals. Deviation of crystal OSC should be expected within 100ppm in room temperature.
**1) a minor fix
Two calls of HAL_GPIO_WritePin() were added to USBH_LL_DriverVBUS(), ''USER CODE'' section, to control VBUS power switch chip.
usbh_conf.h
line: 398
USBH_StatusTypeDef USBH_LL_DriverVBUS (USBH_HandleTypeDef *phost, uint8_t state)
{
/* USER CODE BEGIN 0 */
/* USER CODE END 0*/
if (phost->id == HOST_FS)
{
if (state == 0)
{
/* Drive high Charge pump */
/* ToDo: Add IOE driver control */
/* USER CODE BEGIN DRIVE_HIGH_CHARGE_FOR_FS */
// the enable pin of the power switch chip is active-low
HAL_GPIO_WritePin(OTG_FS_PowerSwitchOn_GPIO_Port, OTG_FS_PowerSwitchOn_Pin, GPIO_PIN_SET);
/* USER CODE END DRIVE_HIGH_CHARGE_FOR_FS */
}
else
{
/* Drive low Charge pump */
/* ToDo: Add IOE driver control */
/* USER CODE BEGIN DRIVE_LOW_CHARGE_FOR_FS */
HAL_GPIO_WritePin(OTG_FS_PowerSwitchOn_GPIO_Port, OTG_FS_PowerSwitchOn_Pin, GPIO_PIN_RESET);
/* USER CODE END DRIVE_HIGH_CHARGE_FOR_FS */
}
}
HAL_Delay(200);
return USBH_OK;
}
2) Tuning of Keep-Alive / SOF interval
You may reduce this interval on the firmware.
Reduce this figure by ONE or TWO.
stm32f4xx_ll_usb.c
line:1222
HAL_StatusTypeDef USB_InitFSLSPClkSel(USB_OTG_GlobalTypeDef *USBx , uint8_t freq)
{
USBx_HOST->HCFG &= ~(USB_OTG_HCFG_FSLSPCS);
USBx_HOST->HCFG |= (freq & USB_OTG_HCFG_FSLSPCS);
if (freq == HCFG_48_MHZ)
{
USBx_HOST->HFIR = (uint32_t)48000U; // <---- 47999U, for full-speed
}
else if (freq == HCFG_6_MHZ)
{
USBx_HOST->HFIR = (uint32_t)6000U; // <---- 5999U, for low-speed
}
return HAL_OK;
}
Tsuneo
