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srtgumbee
Joined: 15 Dec 2018
Posts: 5
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| PWM problem on 18F45K40 |
 Posted: Sun Dec 16, 2018 3:21 pm |
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I'm having issues with the setup and running of the CCP1 PWM on the 18F45K40.
CCS Complier V5.081
The 18F45K40 is a new to me as is the latest compiler version. I have confirmed PWM works with my old 16F1826 and new compiler V5.081.
With the 18F45K40 have confirmed Digital I/Os are working OK, Analogs inputs are OK, I2C is OK, TXD is OK BUT PWM is stopping when at a low duty cycle and not recovering until power is reset.
In the stripped back code below the PWM stopped when it gets to the (long) numbers 17 to 22 (all other number are fine), if I use (int) numbers then it stops when 5 or 6 are used and all other numbers are fine.
The other issue I have (which may be related) is the PWM does not run after a program load using pickit3, it requires a power reset for the PWM to start. Yet immediately after a program load I can see the pic is running as TXD is working (when I had it enabled).
Any tips on this would be appreciated!
| Code: |
#include <18F45K40.h>
#FUSES NOEXTOSC
#FUSES NOMCLR
#FUSES NOBROWNOUT
#FUSES NOWDT
//#use delay(internal = 64M)
#use delay(internal = 16M)
#PIN_SELECT CCP1OUT = PIN_C2
#define TRIS_A_VALUE 0b00010110
#define TRIS_B_VALUE 0b11111111
#define TRIS_C_VALUE 0b10111001
#define TRIS_D_VALUE 0b01111110
#define TRIS_E_VALUE 0b00001000
//#use rs232(baud=9600,xmit=PIN_A3,FORCE_SW, stream = debug)
//#use rs232(baud=9600,xmit=PIN_C6,rcv=PIN_C1, stream = xbee)
void main()
{
//setup_oscillator(OSC_HFINTRC_64MHZ);
set_tris_a( TRIS_A_VALUE );
set_tris_b( TRIS_B_VALUE );
set_tris_c( TRIS_C_VALUE );
set_tris_d( TRIS_D_VALUE );
set_tris_e( TRIS_E_VALUE );
setup_ccp1 (CCP_PWM);
output_drive(PIN_C2);
//setup_timer_2(T2_CLK_MFINTRC | T2_DIV_BY_1, 99, 1);
setup_timer_2(T2_CLK_INTERNAL | T2_DIV_BY_128, 99, 1);
set_pwm1_duty(0);
while( TRUE )
{
long i;
for(i=0; i<99; i++)
{
//fprintf(debug,"i = %lu \r\n", i);
set_pwm1_duty(i);
delay_ms(1000);
}
}
} |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19215
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| Posted: Mon Dec 17, 2018 2:44 am |
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Your startup issue, is almost certainly the hardware limit timer.
T2, on this chip has the ability to be run as a monostable, as well as a
free running timer, and be triggered by external sources. You need to
disable this to have it free run as a conventional timer:
setup_timer_2(T2_CLK_INTERNAL | T2_DIV_BY_128 | T2_START_IMMEDIATELY, 99, 1);
It's probably waking intermittently with the enable off...
It's possible that the control for this is defaulting to a pin that is affected
by the PWM, so this is the other problem as well, though I cannot
immediately see this.
I can't see anything else. You do realise you will only get to a 25% duty
cycle with your numbers?. |
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srtgumbee
Joined: 15 Dec 2018
Posts: 5
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| Posted: Tue Dec 18, 2018 7:19 pm |
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Hi Ttelmah,
Thank you for your reply and hints. Short answer - The PWM on the 18F45K40 is and was always operating correctly!
Based on your information I started investigating the hardware more thoroughly and found the 12V DCDC power supply which was powering my LED was shutting down when PWM was ~5%.
The PIC was running perfectly, but I had no visual output or on the scope and having just tested the same output with a 1hz 'blink led' I was lead down the path the PWM was the cause of my issues.
Thanks again for your contribution, it helped me come to my senses! |
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