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lpc176x: force minimum usb disconnect time 

Fixes GitHub Issue #1499. Resolves USB hang by forcing a minimum
USB disconnection time at boot.

Signed-off-by: Matt Baker <baker.matt.j@gmail.com>
This commit is contained in:
Matt Baker 2019-04-06 15:12:51 -07:00 committed by KevinOConnor
parent 04adde9a02
commit e83071c9fe
3 changed files with 19 additions and 0 deletions
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2
src/lpc176x/internal.h
View File

@ -18,4 +18,6 @@ int is_enabled_pclock(uint32_t pclk);
void enable_pclock(uint32_t pclk);
void gpio_peripheral(uint32_t gpio, int func, int pullup);
void udelay(uint32_t usecs);
#endif // internal.h

15
src/lpc176x/main.c
View File

@ -7,6 +7,7 @@
#include "LPC17xx.h" // NVIC_SystemReset
#include "command.h" // DECL_CONSTANT
#include "sched.h" // sched_main
#include "board/misc.h" // timer_read_time
DECL_CONSTANT_STR("MCU", "lpc176x");
@ -66,6 +67,20 @@ command_reset(uint32_t *args)
}
DECL_COMMAND_FLAGS(command_reset, HF_IN_SHUTDOWN, "reset");
// Implement simple early-boot delay mechanism
void
udelay(uint32_t usecs)
{
if (!(CoreDebug->DEMCR & CoreDebug_DEMCR_TRCENA_Msk)) {
CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;
}
uint32_t end = timer_read_time() + timer_from_us(usecs);
while (timer_is_before(timer_read_time(), end))
;
}
// Main entry point
int
main(void)

2
src/lpc176x/usbserial.c
View File

@ -277,6 +277,8 @@ usbserial_init(void)
gpio_peripheral(GPIO(0, 30), 1, 0);
gpio_peripheral(GPIO(0, 29), 1, 0);
gpio_peripheral(GPIO(2, 9), 1, 0);
// enforce a minimum time bus is disconnected before connecting
udelay(5000);
// setup endpoints
realize_endpoint(EP0OUT, USB_CDC_EP0_SIZE);
realize_endpoint(EP0IN, USB_CDC_EP0_SIZE);