16F876A Pulsin issues

[Bobbo_ZA]

I have an idiot grin on my face, :-) im making some really good progress, I have the pulse in now displaying on the screen (strange from a JR Rx Im getting a range from 560 - 990 from the pulsin) and have the ability to jump to a servo test (sweep from side to side) at the push of a button, :-)

My ADC is sort of working, with the voltage divider I'm getting 2.54V on my DMM, however if I display the ADC input Im only seeing 2 and not the .54 (obviously this will be multiplied by 2 once i get the decimals). I have tried:

lcdout $FE, $C0+8, dec volt

and 

lcdout $FE, $C0+8, # volt

but still only get the first digit. Is this due to the ADC VAR being a "WORD"

Volt    Var     WORD
.
.
.
ADCIN 4, volt
.
.
.

My Vref from the regulator is 5.00V on my DMM

Not sure im getting this whole ADC concept, I;ve read another one of Melanie's posts and from what I can work out, my RAW ADC in variable should be as follows:

if my Vref = 5.00 then if my ADCIN was exactly 5.00V the ADC result would give me 1024, however I am giving a ADC of 2.54 I should get a value in the variable of 520? however I am displaying a single digit "2" on the LCD with the code above, not sure how to do the math on this.

[Bobbo_ZA]

Ah, ok, finally, im a git, :-)

Im now reading a 520 adc value with the battery on and the DMM measuring 2.54 (Needs to be multiplied by 2 to reverse the voltage divider effect).

Err, something not right, im missing something with the math:

    ADCIN 4, volt                  ' Read AN4 into temp variable
    Vin = (5*volt/1024)       ' Convert to voltage assuming 5.00 = 1024

lcdout $FE, $C0+8, dec Vin,".",dec2 Vin,"V"

pulling out many hairs, :-( my biggest issue is that even in school my maths was not great, spose thats why Excel was invented, for people like me, :-)

[Bobbo_ZA]

just not getting the decimal places now, :-(

Latest attempt

ADCIN 4, volt                  ' Read AN4 into temp variable
volt = volt * 2
Vin = (5*volt/1023)
Vind = (volt // 1000) / 10 'millivolts?

lcdout $FE, $C0+8, dec Vin,".",dec2 Vind,"V"

Time to pack it in for the night, work tomorrow, fairly good progress, just the decimal points to figure out.

Kind Regards
Rob

[Bobbo_ZA]

Am I on the right track?

the "//" operator will store the remainder in the chosen Var, thus:

ADCIN 4, volt                  ' Read AN4 into temp variable
volt = volt * 2                 'Correct the ADCin for the Voltage divider?
FVolt = (5*volt/1023)
MVolt = (5*volt // 1023)  'millivolts?

lcdout $FE, $C0+8, dec FVolt,".",dec4 MVolt,"V"

Sorry for getting overly complex with this but trying to understand how it works, I have been able to simulate what I need to do in excel, just not sure if the above will work in PBP:

D1 = Vref @ 5.00
D5 = Adc Corrected @ 1021
D6 = 10 bit ADC @ 1024

D14 = Whole number (Formula =TRUNC(D9,0), result = 4
D15 = Remainder (Formula =(MOD((D5*D1)/D6,1)*1000)), result = 990

I could then LCDout D14, ".", D15 in theory if the formula in PBP equaled the excel result.

not sure though, still a bit confused

Cheers
Rob

[Acetronics2]

just not getting the decimal places now, :-(

Latest attempt

ADCIN 4, volt                  ' Read AN4 into temp variable
volt = volt * 2
Vin = (5*volt/1023)
Vind = (volt // 1000) / 10 'millivolts?

lcdout $FE, $C0+8, dec Vin,".",dec2 Vind,"V"

Time to pack it in for the night, work tomorrow, fairly good progress, just the decimal points to figure out.

Kind Regards
Rob

Ok Rob,

What about :

ADCIN 4, volt                  ' Read AN4 into temp variable

volt = volt * 2 * 5

Volt = 100*volt               ' See manual for DIV32 !!!
Vind = DIV32 1024           ' Here we have result in 1/100 Volts ...

Vin = Vind/100                  ' Here we get the integer part ...
Vind = Vind // 100             ' Here we get the decimal part ...

lcdout $FE, $C0+8, dec Vin,".",dec2 Vind,"V"

that's all !

[Bobbo_ZA]

Cant believe it can be that simple, i was trying to over complicate things, :-)

Will try it again tonight, :-)

Achievements So far:
1. Hitachi LCD interfaced to 16F876A
2. Read input from RC Receiver
3. Drive a Servo from the PIC
4. Display pulsin values on the LCD
5. Measure Flight Pack voltage - with load on demand

Still to do:
1. Menu system for each function
2. separate components into sub functions
3. Move off Breadboard and build into an enclosure of some sort.

List of proposed features:
1. Rc Flight pack battery tester
2. Servo Tester - with Sweep and Centering
3. Current monitor - planing to add either SI210709-300T (50A) or ACS750
4. Receiver Pulse monitor for other PIC projects
5. Thermometer - Although I think I'm all out of AD inputs
6. Sure Im going to come across some more features to add to it, :-) any ideas?

[Bobbo_ZA]

Hi Ace, All,

its working, :-) cant believe it was that simple, :-)

going to start working on the next phase of the implementation this weekend.

Hope everyone has a good weekend, :-)

Cheers
Rob