UM2071 datasheet(47/56 Pages) STMICROELECTRONICS

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UM2071

BlueNRG-1 peripheral driver examples

DocID029370 Rev 3

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MFT timers: this example shows how configure peripherals MFT1, MFT2 and SysTick to

generate three timer interrupts at different rate: MFT1 at 500 ms, MFT2 at 250 ms and

SysTick at 1 second.

15.9

UART examples

DMA: IO8 and IO11 are configured as UART pins and DMA receive and transmit requests

are enabled. Each byte received from UART is sent back through UART in an echo

application (USB-to-SERIAL must be connected to the PC).

Interrupt: IO8 and IO11 are configured as UART pins and receive and transmit interrupts

are enabled. Each byte received from UART is sent back through UART in an echo

application (USB-to-SERIAL must be connected to the PC).

Polling: IO8 and IO11 are configured as UART pins. Each byte received from UART is

sent back through UART in an echo application (USB-to-SERIAL must be connected to the

PC).

15.10

WDG examples

Reset: demonstrates the watchdog functionality and using it to reboot the system when the

watchdog interrupt is not serviced during the watchdog period (interrupt status flag is not

cleared).

The watchdog is configured to generate the interrupt with a 15 s interval, then it is enabled

and monitors the state of the PUSH1 button (IO13 pin). Any change on this pin triggers the

watchdog counter to reload and restart the 15 s interval measurement.

If the IO13 pin state does not change during this interval, the watchdog generates an

interrupt that is intentionally not cleared and therefore remains pending; the watchdog

interrupt service routine is therefore called continuously and the system is stuck in the

watchdog interrupt handler.

The chip is reset as it can no longer execute user code. The second watchdog timeout

triggers system reboot as a new watchdog interrupt is generated while the previous

interrupt is still pending. The application then starts measuring the 15 s interval again.

The three user LEDs are toggled at increasing frequencies until the board is reset or

PUSH1 button is pressed, which restores the LEDs toggling frequency with the 15 s

watchdog timer.

Wakeup: The watchdog timer is a 32-bit down counter that divides the clock input (32.768

kHz) and produces an interrupt whenever the counter reaches zero. The counter is then

reloaded with the content of the WDT_LR register. If the interrupt status flag is not cleared

and a new interrupt is generated, then the watchdog may generate a system reset.

This example demonstrates the use of the watchdog to periodically wake the system from

standby mode using the watchdog interrupt. The watchdog is configured to generate the

interrupt at 1 s intervals. The watchdog is then enabled and the system is switched to the

standby mode. As soon as the watchdog interrupt is generated, the system wakes up,

LED1 (IO6 pin) is toggled and the device returns to standby mode. The IO6 pin is therefore

toggled every 1 s.

UM2071 Datasheet(PDF) 47 Page - STMicroelectronics

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