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cpu/stm32/periph/usbdef_fs: emulate disconnect/connect

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If the MCU does not have an internal D+ pullup and there is no dedicated GPIO to simulate a USB disconnect, the D+ GPIO is temporarily configured as an output and pushed down to simulate a disconnect/connect cycle to allow the host to recognize the device. However, this requires an external pullup on D+ signal to work
This commit is contained in:
Gunar Schorcht 2022-10-12 11:14:18 +02:00
parent 58ebf02e58
commit add766f3e1
1 changed files with 14 additions and 0 deletions
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14
cpu/stm32/periph/usbdev_fs.c
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@ -31,6 +31,8 @@
#include "periph/usbdev.h"
#include "usbdev_stm32.h"
#include "pm_layered.h"
#include "ztimer.h"
#include <string.h>
/**
* Be careful with enabling debug here. As with all timing critical systems it
@ -147,6 +149,18 @@ static void _enable_usb_clk(void)
static void _enable_gpio(const stm32_usbdev_fs_config_t *conf)
{
if (conf->af == GPIO_AF_UNDEF && conf->disconn == GPIO_UNDEF) {
/* If the MCU does not have an internal D+ pullup and there is no
* dedicated GPIO on the board to simulate a USB disconnect, the D+ GPIO
* is temporarily configured as an output and pushed down to simulate
* a disconnect/connect cycle to allow the host to recognize the device.
* This requires an external pullup on D+ signal to work. */
gpio_init(conf->dp, GPIO_OUT);
gpio_clear(conf->dp);
/* wait a 1 ms */
ztimer_sleep(ZTIMER_MSEC, 1);
gpio_init(conf->dp, GPIO_IN);
}
if (conf->af != GPIO_AF_UNDEF) {
/* Configure AF for the pins */
gpio_init_af(conf->dp, conf->af);