Software description

AN3413

10/18

DocID018933 Rev 2

2

Software description

2.1

STM32L1x peripherals used by the application

This application example uses the following STM32L1x peripherals with the settings

described below:

ADC

current.

•

ADC resolution: 12-bit

•

ADC conversion mode: single

•

ADC sampling time: 192 cycles

SYSTICK Timer

The Systick timer is used to generate the delay needed for display or wait loops.

GPIOs

Port C and Port E are connected to the USER push-button and the LEDs.

•

PB1 set as an input floating pin with interrupt connected to the USER push-button

•

PB7 (green LD3) and PB6 (blue LD4) set as an output push-pull

•

PA0 set as a wake-up pin configured either as an input floating pin with interrupt with

detection on rising edge or as an alternate function AFIO0 (WKUP1) during Standby

mode.

•

PA6, PA7, PC4, PC5, PB0, PB1 are used for linear touch sensor or touchkeys during

the touch sensor demonstration.

•

During the low power modes, I/Os are placed in analog input mode to reduce power

consumption except for a few pins related to the hardware interface (PB7 - green LD3

timer enable). This means that all Schmitt triggers on unused standard I/O pins are

disabled to reduce power consumption.

LCD controller

The different functions available in the firmware library for LCD are used to initialize, clear,

display strings and scrolling messages needed in the application code. For some low power

mode measurements, the LCD controller is turned OFF to minimize the current consumption

of the STM32L152.

Clock

The MSI (the multi speed internal oscillator) oscillator is selected as clock source. The

application manages the peripheral clocks depending on the selected power saving mode.

When the device enters low power run mode, MSI is switched to range 0 until the device is

woken-up by an external event. When exiting Low power run mode, the MCU switches the

HSI oscillator back ON. LSE is switched ON during Manufacturing test mode (see

Section 1.5.3) to check its functionality.