\ Program Name: freq-gen.txt
\ Hardware: STM32F0 Discovery board which runs Mecrisp-Stellaris for the stm32f051 at 8 Mhz using the RC clock
\ Author:  t.porter <tery@tjporter.com.au> November 2016
\ All register names are CMSIS-SVD compliant so use Svd2forth-v2 to generate your memory map words or use freq-gen-memap.txt which is included in this project.

\ Overall Design
\ Registers used: GPIOB, TIM14
\ Timer = tim14
\ Tone output pin: PB-1


\ init words
: tim14-cc1e-as-output %1  0 lshift TIM14_CCER bis! ;		\ TIM14_CC1E 
: tim14-clock-enable %1  8 lshift RCC_APB1ENR bis! ;		\ TIM14 clock enable
: tim14-pwm_mode    %110  4 lshift TIM14_CCMR1_Output bis! ;	\ TIM14_OC1M 110: PWM mode 1 
: tim14-start %1  0 lshift TIM14_CR1 bis!  ;			\ TIM14_CCR1 counter enable (start timer)
: pb1-af0 %10  2 lshift GPIOB_MODER bis! ;			\ GPIOB_MODER1

\ program words
: pulse-length  TIM14_ARR ! ;	\ set frequency
: duty-cycle  TIM14_CCR1 ! ;	\ set duty cycle

: arr 				\ auto reload register value (frequency at 50% duty cycle (800 = 10.06khz))
dup dup pulse-length
." TIM14_ARR is $" hex. cr
shr				\ pulse-length divided by 2 for 50% duty cycle
duty-cycle
;

: hz DUP ." for a output of " . ." Hz (CLOCK = 8MHz, Prescaler = 0) " 8000000 swap / arr  ;
\ 123 Hz (minimum) = $FE10, 15Khz = $215, 20Khz = $190, 350KHz (max) = $16


\ init 
tim14-clock-enable
tim14-cc1e-as-output
tim14-pwm_mode
tim14-start
pb1-af0

\ output a 5 KHz square wave on PB-1
5000 hz			    \ 5025 Hz at 50.25% duty cycle



\  Screenshot:-
\ Forth> 20000 hz
\ -> 20000 hz
\ <- for a output of 20000 Hz (CLOCK = 8MHz, Prescaler = 0) TIM14_ARR is $00000190
\ <- ok.