Cannot get scaling function work: RESOLVED

[iDeeW]

Hi everyboy,

I just started GCBasic. I wrote some code to read a Microchip MCP3428 ADC chip over i2c.
Basically my library returns ADC value as an integer value. i2c code works great.
But when I try to scale, it returns a byte value (0 to 255).
But I expect a number 0 to 32767. What am I doing wrong here?

    read = MCP342x_convert_oneshot(2, , , err)
    HSerPrintStringCRLF str(read)' here 0 to 32767 value is returned as expected
    read = scale( read, 0, 32767, 0, 3000)
    HSerPrintStringCRLF str(read)' here I see a 0-255 value, not what I expects

Thank you

[Anobium]

My guess, a total guess as I do not the code segment about.

Try adding #option explicit to your USER program not the .h

Then, I am guessing, but read is a byte.... should be a word?
read = MCP342x_convert_oneshot(2, , , err) this returns an?
and,
read = scale( read, 0, 32767, 0, 3000) this is an Integer or Word? and, you want the returnd range to be between 0 and 3000?

The .h
Lovely clean code. Very nice.
And, check... line 81... missing brace!
And, check .. line 81... can you return an out_err? Hard code an out_err and make sure this is working.

So, a few things to check.

[iDeeW]

Thank you so much for the quick reply.
The function MCP342x_convert_oneshot(2, , , err) returns an integer
and read is defined as integer.
Acording to the documantation scale function returns an integer.
You are correct, I'm expecting a number from 0 to 3000 after scaling.

But even with #option explicit my serial turminal shows a 0 to 255 number after scaling.

I'm really confused...

[Anobium]

You will have to post the complete project. New .h as well.

But, try this comment out the MCP call. Hard code the read value, first as 0 then as 32767, what happens? Is scale returning 0 and 3000?

[Anobium]

You will have to post the complete project. New .h as well.

But, try this comment out the MCP call. Hard code the read value, first as 0 then as 32767, what happens? Is scale returning 0 and 3000?

[iDeeW]

#chip pic16f877a, 16
#option explicit

'include files
#include <maths.h>              ;required maths.h
#include <MCP342x.h>
#include <MCP4725.h>

'defines LCD Settings
#define LCD_NO_RW 'Needed when RW is grounded
#define LCD_IO 4  'Mode
#define LCD_RS PORTB.0    '
#define LCD_Enable PORTB.1
#define LCD_DB4 PORTB.4
#define LCD_DB5 PORTB.5
#define LCD_DB6 PORTB.6
#define LCD_DB7 PORTB.7
'dir Portb.2 in   ' Backlight on

'define I2C settings
hi2cmode Master 'I2C MASTER MODE
#define HI2C_BAUD_RATE 400
#define HI2C_DATA PORTC.4
#define HI2C_CLOCK PORTC.3
dir HI2C_DATA in
Dir HI2C_CLOCK in

'Serial Port Settings
#define USART_BAUD_RATE 19200
#define USART_TX_BLOCKING
#define USART_DELAY 0 ms
dir PORTC.6 Out

'Variables
dim err as Integer
dim read as Integer
dim adc_val as String

start: 'Main Loop Start here
 'if MCP342x_available then
      locate 0,0: print "Inp Volt:"
      locate 0,10: printVol(): print "V"
      locate 1,0: print "Out Curr:"
      locate 1,10: printCur(): print "A"
 'end if
 'if MCP4725_available then
      MCP4725_set_voltage(250)'0 to 4095
 'end if
  wait 200 ms
goto start

sub printVol()
  read = MCP342x_convert_oneshot(2, , , err)
  HSerPrintStringCRLF str(read)
  read = scale( read, 0, 32767, 0, 3000)
  HSerPrintStringCRLF str(read)
  print str(read)
end sub

sub PrintCur()
  read = MCP342x_convert_oneshot(1, ,8 , err)
  if read > 32767 then read = 0
  adc_val = leftpad(str(scale([Integer]read, 0,6403 , 0, 5000)), 4, "0")
  print left(adc_val, 2)+ "." + right(adc_val, 2)
end sub

[Anobium]

Will not compile. Missing .h = MCP4725.h

#include <MCP342x.h>
#include <MCP4725.h>

[Anobium]

I have worked around.

What I know:
1. The scale function is working as expected, as are the string methods.
2. Returning 0 and 32767 from MCP342x_convert_oneshot provides the correct results of 0 and 32767 and the PrintVol and PrintCur handle these tests correctly.

Do this.

Line 137: MCP342x_convert_oneshot = FnLSL([word]Value1, 8)+ Value2. Hard code values here that are meaningful values and test. I cannot test as I dont have this sensor. I think the value being returned from MCP342x_convert_oneshot is not what you expect. So, we need to look carefully in this method.

Test and let me know what happens.

Also, ONLY DO THIS ONCE WE HAVE THE VALUE RETURNED CORRECTLY. Consider this. Remember, I do not know this sensor.. so, check my thinking.

'add - the may work better
dim Returned_Value as integer 
dim sersor_state as byte

HI2CSend  MCP342x_AddrRead
  HI2CReceive Value1,  MCP342x_convert_oneshot_h
  HI2CReceive Value2,  MCP342x_convert_oneshot
  HI2CReceive Value3,  sersor_state
  HI2CStop
  set config.7 off
  if sersor_state = config then
    'err = -100 'One-shot Config Error
  end if

Anobium

[iDeeW]

I tested the library function just like you asked. It returns expected values.
Below is what I am seeing right now.

sub printVol()
      Dim readv as integer
      readv = MCP342x_convert_oneshot(2, , , err)'....here 30V input to ADC
      print str(readv)'...............................LCD shows value 32767
      print " "
      readv = scale(readv, 0, 32767, 0, 30000)'......expected value is 30000
      print str(readv)'...............................but LCD shows value 48
end sub

[Anobium]

Post the complete project. As I get 32767 30000 when I use the following code. I just hard coded the 32767 in your method.

Try this code. What value do you get?

Puzzled

Anobium

  #chip 16f877a, 20

  #define LCD_NO_RW 'Needed when RW is grounded
  #define LCD_IO 4  'Mode
  #define LCD_RS PORTB.0    '
  #define LCD_Enable PORTB.1
  #define LCD_DB4 PORTB.4
  #define LCD_DB5 PORTB.5
  #define LCD_DB6 PORTB.6
  #define LCD_DB7 PORTB.7

  printVol

   sub printVol()
      Dim readv as integer
      readv = 32767   'MCP342x_convert_oneshot(2, , , err)'....here 30V input to ADC
      print str(readv)'...............................LCD shows value 32767
      print " "
      readv = scale(readv, 0, 32767, 0, 30000)'......expected value is 30000
      print str(readv)'...............................but LCD shows value 48
end sub

[Anobium]

Is this the cause?

StrInteger() not Str()

[iDeeW]

I agree, this is very puzzling...!
I tried the below code with StrInteger& it behaves exactly the same.

sub printVol()
  dim readv as Integer
  readv = MCP342x_convert_oneshot(2, , , err)'....here 30V input to ADC
  'if readv < 0 then readv = 0
  print StrInteger(readv)'..LCD shows value 32767. which is what I expects
  print " "
  readv = readv * 30000 / 32767'......expected value is 30000
  'readv = scale(readv, 0, 32767, 0, 30000)'...this prints value 48 on LCD
  'adc_val =  leftpad(StrInteger(readv), 5, "")+ "mV"
  print StrInteger(readv)'.........................This prints value 0 on LCD
end sub

Its not the scaling function!
What am I doing wrong?
Thanks,

[Anobium]

Do this.

---

Line 137 of MCP342x.h. Hard code a value of 16383
MCP342x_convert_oneshot = 16383
Test - what is the result? 15000?

---

If the above test returns 15000 , then, line 133 is the same file is not returning what you think. So Value3 is not return a config - to proove this add this to line 139. So, to test is value is not equal to config. Do this.

MCP342x_convert_oneshot =32767
Test - what is the result?

---

Then, I would get the protocol analyser out.

[iDeeW]

I hardcoded 16383......function returns 16383 but LCD shows 151

---

I change the else side to return MCP342x_convert_oneshot =32767, but the function still returns 16383 & LCD shows 151.
Edited library file is attached...

---

I have my Logic Analyser hooked up.... all return values looks good and match with the datasheet.

[iDeeW]

[Anobium]

Got an update?

[iDeeW]

I created a new file and rewrote the whole code (used the same library files) & it started working...yay!

Is it possible the old project file was somehow currupted??

Thanks

[Anobium]

Post the code - may be we can spot the original condition but there is no cache of code. Each compile is unique and all new ASM is generated... it would be good to figure out the root cause.

[iDeeW]

Attached.

Thanks

[Anobium]

Cheers.

1. So, what is the MCP3428 ? and, the MCP4725? What do they do?
2. Should we take you code and create a demo and two libraries?
3. Why two libraries? This may be obvious when #1 is ansered. :)

[iDeeW]

MCP342x is a ADC and the MCP4725 is a DAC from Microchip.
Once I add all the functionalities, I will definitely share the libraries.
Thanks

[Anobium]

I see. So, hence the two libraries. Make a lot more sense now.

Be good to have 'similar' ADC commands like READAD16_MCP32xx. An idea.

[iDeeW]

Great idea...will do.

Thanks

[Pic Fan 1975]

any progress on making a library for MCP4725?

[Anobium]

@PIC FAN 1975

See https://sourceforge.net/p/gcbasic/discussion/projects%26guides/thread/bd4ae4f713/ for MCP4725.

Took me longer to write up than do the programming. :-)