AN3151

Firmware implementation

Doc ID 17051 Rev 1

17/34

5

Firmware implementation

Below are some details of firmware implementation.

It's not an exhaustive firmware implementation description but it mainly focuses on some

important microcontroller settings: TIM1, ADC and PI controller implementation.

The firmware developed for the LED Streetlight application is based on STM8S firmware

library release 1.1 and entirely downloadable from the internet.

The firmware described in this application note is entirely available; to obtain a copy please

contact your closest ST office.

5.1

Basic initialization of peripherals and I/O pins

At the beginning of the main program, all the peripherals and I/O pins are configured as

described below:

●

The Clock source is selected in order to have the maximum frequency by means of an

external 24 MHz oscillator.

●

GPIO PINs are configured for: ADC channels (floating input) and I/Os.

●

TIMER (TIM1) configuration: Ch1, Ch2, Ch3, and Ch4 are configured in center aligned

mode and provide an AD triggering signal to ADC for conversion by TRGO.

●

ADC Configuration: AIN8, AIN9, AIN10, AIN11, and AIN12 are converted one by one

during the “update” event forced by TIM1. Single shot conversion has been set.

Other firmware settings are for interrupt and joystick/pushbutton management. The joystick,

soldered onto the control section, is useful in debug phase to change the PI gains.

This feature is implemented on a low priority interrupt.

5.2

Peripheral settings

The main peripheral settings are:

●

Clock configuration

●

TIM1 configuration

●

ADC configuration

The clock configuration is related to the PRESCALER by means of the function:

/* Configure the Fcpu to DIV1*/

CLK_SYSCLKConfig(CLK_PRESCALER_CPUDIV1);

The TIM1 configuration is:

TIM1_DeInit();

TIM1_TimeBaseInit(0,TIM1_COUNTERMODE_CENTERALIGNED1, PWM_PERIOD,5);