Voltage to frequency converter with PIC

[Andy_123]

Got 18F242 today !

Need some help with configuration statement(s) - equvalent to
__config 0x3d3a for 16F870

I see qute a few registers there...

 

[motion]

Avoid using "magic numbers" when specifying constants.

     LIST         P = PIC18F242, F = INHX32, R = DEC
     INCLUDE      "P18F242.INC"

 __CONFIG _CONFIG1H, _HSPLL_OSC_1H
 __CONFIG _CONFIG2L, _BOR_OFF_2L&_PWRT_OFF_2L
 __CONFIG _CONFIG2H, _WDT_OFF_2H
 __CONFIG _CONFIG3H, _CCP2MX_ON_3H
 __CONFIG _CONFIG4L, _STVR_ON_4L&_LVP_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, _WRTC_OFF_6H&_WRTB_OFF_6H&_WRTD_OFF_6H
 __CONFIG _CONFIG7L, _EBTR0_OFF_7L&_EBTR1_OFF_7L&_EBTR2_OFF_7L&_EBTR3_OFF_7L
 __CONFIG _CONFIG7H, _EBTRB_OFF_7H

 

[Andy_123]

Thanks,
This configuration is a little different than 16F... :lol:

Last night I got 18F242 interrupt program working - no analog section yet.
I am using 20MHz resonator for now.
Looking at the scope I should be able to have room for main program at 50KHZ. will do more tests and post results.

 

[motion]

Almost forgot. The above configuration applies to a 4X HS PLL oscillator (i.e. 40Mhz).

 

[Andy_123]

I saw this,
I was using HS type when I set conf mannualy...
I just don't has 40MHz crystal yet.

I plugged 18F242 to the same breadboard circuit i have for 16F870 and it worked.
I will try to post scope snapshots tonight.
So far I got divider as low as 000C with 1:2 timer clock.
This gives me 50KHz and about 15-18 clocks in the main program to handle analog inputs. The way I am doing this:
I am looping the main program and toggling another port:

LOOP01:
negf LATB,0
GOTO LOOP01

I am using port C for pulse train generation and port B for diagnostics.
This loop takes 3 clocks or 600ns on the scope, so I can see interrupts on 2 channel oscilloscope.

600ns/3=200ns => 5 MHz * 4 => 20MHz crystal...

 

[Andy_123]

Just a quick update:
I still can't run 18F242 at 40MHZ - I don't have 10MHZ Crystal yet.
It actually work just fine with 12MHZ Crystal (48MHZ), but I don't want to overclock it yet.

So I am running it at 20MHZ (HS mode) for now and spent some time on analog conversion.
I am not doing sampling/avaraging yet - just simple read.
Presets are taken form the table - 1024 DW values generated in excel and pasted into asm program.

Works fine but I did no extensive testing yet. I will post code in a couple days.