Oscillator question and measurement

[Christopher4187]

I only had a PIC in a QFN package but wanted to make a protoype with it. What I did was strip a 24 gauge wire and solder each individual strand to each pin. I'm never doing that again but.....

It seems slower than what it should be. I want to determine if it's the hardware or software so I used this:

Start:
TOGGLE portd.1
PAUSEUS 1
GOTO start

I have a 20 MHz crystal and DEFINE OSC 48. When I measure the frequency, am I supposed to get 1MHz? I get about 374 KHz. One thing that may be causing this is, to stabilize the soldering, I put hot glue on all of the pins not realizing that it's probably putting a little resistance between the oscillator pins.

Any ideas?

[rsocor01]

Hi,

Get rid of the line "PAUSEUS 1" and tell us what happens.

[Acetronics2]

some JELT pcb " Tropicoat " protective varnish makes real good glue ... did you also try nail lacquer ??? ( NO metallic colour !!! - of course -)

a simulator run would show your program NEVER will run @ 1 Mhz ... as TOGGLE and GOTO commands need some time to execute

we also must suppose your Pic is a 18F series for the Pauseus1 to be equal to 1µs ...

Now, Hot glue doesn't disturb the oscillator in any way ...

Alain

[Christopher4187]

Get rid of the line "PAUSEUS 1" and tell us what happens.

I didn't have a scope handy and the meter I had isn't able to calculate high frequencies. I'll be able to try that tonight. What should I expect to see with just a toggle command?

we also must suppose your Pic is a 18F series for the Pauseus1 to be equal to 1µs ...

Yes, it's an 18F4550. The program works but the CAN data isn't flowing smoothly compared to the previous devices I made. All of the pinouts are different, and wanted to rule that out, but I can't even see how that would cause slow CAN data in the first place.

[Acetronics2]

a little MPSIM ( MPLAB ) simulation - supposed to be relatively true - gives à 3.2µs half -cycle to your test ... around 160 khz output frequency !
BTW ... I'm not sure the DEFINE OSC 48 and a 20 Mhz Xtal to be a good combination ...

best result @ 1.8µs half cycle given by

Portb.1 = ! Portb.1

instead of TOGGLE + PAUSEUS1

[Christopher4187]

Here are the results. Are these typical?

start:
pauseus 1
toggle portd.1
goto start

375 KHz

start:
toggle portd.1
goto start

1 MHz

start:
Portb.1 = ! Portb.1
goto start

This does nothing

start:
portd.1=1
portd.1=0
goto start

3 MHz

[Acetronics2]

start:
Portb.1 = ! Portb.1
goto start

This does nothing

Sure it does not show anything on portD1 ...

Alain

[Christopher4187]

I know. I was too lazy to edit it yesterday. My original comment still stands.

[Acetronics2]

ohhh ... may be the RMW issue ...

due to a 18F chip ... I should have written:

start:
latb.1 = ! latb.1
goto start

on test with the EP5 tomorrow morning ...

[rsocor01]

I didn't have a scope handy and the meter I had isn't able to calculate high frequencies. I'll be able to try that tonight. What should I expect to see with just a toggle command?

I think the problem is that you are not configuring the fuses of the PIC correctly. Are you also setting the OSCON register? I use a 4MHz crystal with my 18F4550 and to make it work the first time it was a pain.

[Acetronics2]

Results of the test ...

output freq is exactly that expected ... and that MPSIM shows ....

111.1 Khz with a 8 Mhz Xtal
277.7 Khz with a 20 Mhz Xtal

sooo ... getting 1 Mhz output looks a bit too much !!! - gives 72 Mhz @ Clock - 18Mhz Xtal and PLL x 4 ; that looks real hard overclocking for such chips ...
MAY BE POSSIBLE, but with very light loads on the output ...

Alain

[Acetronics2]

Results of the test ...

output freq is exactly that expected ... and that MPSIM shows ....

111.1 Khz with a 8 Mhz Xtal
277.7 Khz with a 20 Mhz Xtal
666.5 Khz with 48 Mz @ Clock
833.1 Khz with ... 60Mhz ( poor USB clock ! )
looks a bit over 1Mhz with ... 80Mhz ( poor ... etc )

#CONFIG

    __CONFIG    _CONFIG1L, _PLLDIV_3_1L & _CPUDIV_OSC1_PLL2_1L & _USBDIV_2_1L  
                            ;              ;                      ; USB clock source comes from the 96 MHz PLL divided by 2
                            ;              ; [OSC1/OSC2 Src: /1][96 MHz PLL Src: /2]
                            ; 1/2 prescale 


    __CONFIG    _CONFIG1H, _FOSC_HSPLL_HS_1H & _FCMEN_OFF_1H & _IESO_OFF_1H 
                            ;                  ;               ; Oscillator Switchover mode disabled
                            ;                  ; Fail-Safe Clock Monitor disabled
                            ; HS oscillator, PLL enabled, HS used by USB
    __CONFIG    _CONFIG2L, _PWRT_ON_2L & _BOR_ON_2L  & _BORV_2_2L  & _VREGEN_ON_2L   
    __CONFIG    _CONFIG2H, _WDT_OFF_2H 
    __CONFIG    _CONFIG3H, _MCLRE_ON_3H & _LPT1OSC_OFF_3H & _PBADEN_OFF_3H & _CCP2MX_ON_3H 
    __CONFIG    _CONFIG4L, _STVREN_ON_4L & _LVP_OFF_4L & _ICPRT_OFF_4L  & _XINST_OFF_4L & _DEBUG_OFF_4L
      
    __CONFIG    _CONFIG5L, _CP0_OFF_5L & _CP1_OFF_5L & _CP2_OFF_5L & _CP3_OFF_5L
    __CONFIG    _CONFIG5H, _CPB_OFF_5H & _CPD_OFF_5H
    __CONFIG    _CONFIG6L, _WRT0_OFF_6L & _WRT1_OFF_6L & _WRT2_OFF_6L & _WRT3_OFF_6L 
    __CONFIG    _CONFIG6H, _WRTB_OFF_6H & _WRTC_OFF_6H & _WRTD_OFF_6H 
    __CONFIG    _CONFIG7L, _EBTR0_OFF_7L & _EBTR1_OFF_7L &_EBTR2_OFF_7L &_EBTR3_OFF_7L 
    __CONFIG    _CONFIG7H, _EBTRB_OFF_7H    

         
#ENDCONFIG

trisa = 0
trisb = 0
trisc = 0
trisd = 0
lata = 0
latb = 0
latc = 0
latd = 0

Start:
Latb.1 = ! Latb.1
GOTO start
END

some surely will throw me everything that can fly .... LOL !

sooo ... getting 1 Mhz output looks a bit too much though !!! - gives 72 Mhz @ Clock - 18Mhz Xtal and PLL x 4 ; that looks real hard overclocking for such chips ...
MAY BE POSSIBLE, but with very light loads on the output ...

I did it ... so any idiot can do it too ...

the 4550 did not die ... really nice chip, isn't it ???

Alain

PS: this "timeout" really is a shame, Lester ....