AN3260

Software description

Doc ID 17836 Rev 1

11/24

4

Software description

4.1

STM8S peripherals used by the application

The thermometer application software does not use STM8S standard firmware library. It

rather consists in optimized code by using direct register accesses to control and use the

STM8S general purpose peripherals as described below:

G

CLK

The clock controller enables and delivers the correct clock frequency to the CPU and

peripherals. It configures the HSE clock as the 16 MHz master clock source and the

CPU clock prescaler division factor to 1.

G

GPIOs

The STM8S GPIOs are used to switch on and off LD1, and to configure PA3 and PA4 to

interface with pushbuttons.

G

EXTI

The external interrupt sensitivity is configured to trigger an interrupt each time a falling

edge and only a falling edge, is detected on PA3 or PA4.

G

Flash memory

The minimum and maximum temperature values over one-hour period are saved in the

data EEPROM for further display on the terminal window.

G

UART2

UART2 is used to communicate with the PC terminal software. It is configured as

follows:

–

Baud rate = 9600 baud

–

Word length = 8 bits

–

One stop bit

–

No parity

–

Receive and transmit enabled

–

UART2 clock disabled

Communications are managed by polling each receive and transmit operation on the

UART2 peripheral.

G

ADC1

Channel 2 of the ADC1 is used to convert the analog data issued from the LM235 to

digital values out of which the microcontroller can compute the current temperature

value.

G

Timer 3 (TIM3)

This peripheral is used to generate a 50-ms timebase and to trigger a temperature

acquisition every 50 ms.