Thx Rob for the feedback!
Well. I've checked the hardware, I have a PCB manufactured in lab, A4 goes
to a connector only.
I suspect a defective chip. It also has a weird behavior on PWM.
There are five registers to be written to get the standard PWM mode as
shown in the code below.
The PWM clock source was set to Fosc (PWM1CLKCON_CS = 00)
That is meaning according to my understanding that changing the Foc from
8Mhz to 32MHz and keeping the PWM registers unchanged, the PWM frequency
will increase 4 times on 32Mhz compared with 8 Mhz.
However, the frequency reamains exactly the same, 10KHz at 8Mhz or 32Mhz (
verified on RA4) so the PWM clock arhitecture from datasheet seems to be
wrong, or the chip is bad.
PWM1CLKCON = 0b00000001 -- No prescaler, divide clk source by 1
PWM1CON = 0b11000000
PWM1PH = 800 --100uS, 0.5duty
PWM1DC = 1600 ; PWM1_duty = (PWM1DC - PWM1PH)/(PWM1PR+1)
PWM1PR = 1600 ; PWM1_period = (PWM1PR + 1)*prescaler/ PWM1CLK
; PWM1CLK = 1/(target_clock/4) = 0.5uS at 8MHz
On Sun, Dec 15, 2024 at 4:41 PM Rob Hamerling <[email protected]>
wrote:
>
> Just tested the jallib blink sample (which is running at 4 MHz). At pin_A4
> see a freq. of 0.998 MHz. So it seems like you have a hardware/wiring
> problem..
>
> On 14-12-2024 12:15, vsurducan wrote:
>
> Hi Rob,
> I'm trying to understand the PWM in PIC12F1572, for which the pwm library
> can not be used.
>
> I need to see the system clock.
> The problem is that I can not make it visible on clockout pin. The
> following code should do it?
>
> include 12f1572 -- target PICmicro
> --
> ;pragma target clock 32_000_000 -- oscillator frequency
> pragma target clock 8_000_000 -- oscillator frequency
> --
> pragma target OSC INTOSC_NOCLKOUT -- internal oscillator
> pragma target PLLEN DISABLED -- PLL off
> pragma target CLKOUTEN ENABLED -- clock output enabled
> pragma target WDT DISABLED -- watchdog
> pragma target BROWNOUT DISABLED -- no brownout reset
> pragma target LVP ENABLED -- low voltage programming
> pragma target MCLR EXTERNAL -- external reset
> --
>
> OSCCON_SCS = 0 -- select primary oscillator
> OSCCON_IRCF = 0b1110 -- 8 MHz
> ;OSCCON_SPLLEN = ENABLED -- software PLL on 8x4=32MHz
> OSCCON_SPLLEN = DISABLED - 8Mhz OSC
> --
> enable_digital_io() -- make all pins digital I/O
> pin_A4_direction = output ; output osc/4
> --
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>
> --
> *Rob H*amerling, Vianen, NL
>
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