Digital Pot MCP41010

[cxiong]

I am trying to control the digital pot and it won't work, when I measure the PW0 it is 2.33V, I've try to change the value by writing the setting through RS 232 port and the voltage won't change. But when I read it back what I just enter to the pot, it read back ok.

My program is follow, please help.


------------------------------------------------//////////////////////////////////////////////////////////////////////////////////////
/// //
/// //
/// //
/// Digital Pot control MCP41010 //
///
///
///
/// ---------
/// | 1 |-B0------------
/// | 6 | | ---------
/// | F | |--CS---| 4 |
/// | 8 |-C3-------------- SCK---| 1 |
/// | 7 | | 0 |
/// | 7 |-C5---------------SI---| 1 |
/// | | | 0 |
/// --------- ---------
///
/////////////////////////////////////////////////////////////////////////////////////


#include <16f877.h>
#fuses XT,NOWDT,NOPROTECT,NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7) // Jumpers: 8 to 11, 7 to 12


#include <input.c>
#define CS (PIN_B0)

void main()
{

byte value,cmd;

output_low(CS);

while(true)
{
printf("\r\nRead or Write: ");
cmd=getc();
cmd=toupper(cmd);
putc(cmd);
while ( (cmd!='R') && (cmd!='W') );

if(cmd=='R')
{
printf("\r\nValue: %X\r\n",SPI_READ( ) );
}
if(cmd=='W')
{
printf("\r\nNew value: ");
value = gethex();
printf("\n\r");
SPI_WRITE(0X13);
SPI_WRITE(value );
}
}

}

[cxiong]

Here is the latest, it still not work.

//////////////////////////////////////////////////////////////////////////////////////
/// //
/// //
/// //
/// Digital Pot control MCP41010 //
///
///
///
/// ---------
/// | 1 |-B0------------
/// | 6 | | ---------
/// | F | |--CS---| 4 |
/// | 8 |-C3--------------SCK---| 1 |
/// | 7 | | 0 |
/// | 7 |-C5---------------SI---| 1 |
/// | | | 0 |
/// --------- ---------
///
/// _CS connect to RB0 ** Active Low
/// SCK connect to RC3
/// SI connect to RC5
/// PA0 connect to +5V
/// PB0 connect to GND
/// PW0 connect to Voltmeter.
///
/////////////////////////////////////////////////////////////////////////////////////


#include <16f877.h>
#fuses XT,NOWDT,NOPROTECT,NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7) // Jumpers: 8 to 11, 7 to 12


#include <input.c>
#define CS (PIN_B0)




void main()
{

byte value,cmd,spi;

output_high(CS);
setup_spi(SPI_MASTER | SPI_CLK_DIV_4);
while(true)
{
printf("\r\nRead or Write: ");
cmd=getc();
cmd=toupper(cmd);
putc(cmd);
while ( (cmd!='R') && (cmd!='W') );

if(cmd=='R')
{
spi = SPI_READ();
printf("\r\nValue: %X\r\n",spi );
}
if(cmd=='W')
{
printf("\r\nNew value: ");
value = gethex();
printf("\n\r");
output_low(CS);
SPI_WRITE(0X13);
SPI_WRITE(value );
}
}

}

[ajt]

Try these:

[cxiong]

Do I need to do the samething to read the pot value?

example:

:
:
output_low(CS);
spi_write(0x13); ??? Do I need this line to read the current pot value?
spi=spi_read();
output_high(CS);
:
:
Please advice.

[ajt]

A reading of the spec sheet for the part will show that it does not have a read command. The spec lists these commands:
1. Write a new value to the potentiometer data
register(s).
2. Cause a channel to enter low power shutdown
mode.
3. NOP (No Operation) command.


Why do you want to read the value? You wrote it into the part so you know what it is.
_________________
Al Testani

[cxiong]

I want to read it because everytime I power cycle the unit, the pot value is change/reset(previous enter value) was gone, I have to enter the value everytime.

I would like to do read to see if its value still active. Beside that there is a
SPI_READ() function in the compiler manual.

Give me direction of how to keep the entered value all times unless I decide to change.

[Mark]

This is why I hate it when people double post!

You can't read the value from the pot. You could ask as many people as you like but the fact remains that you can't do it. See here for why:

http://www.ccsinfo.com/forum/viewtopic.php?t=20243

[ajt]

[Ttelmah]

[cxiong]

Thanks for every one's input. I will try to use the EEPROM to
record the pot setting. I will search to see if there is any good
subroutine that I can use specially the EEPROM.

If anyone has a subroutine that work, please let me know.
I plan to use the internal EEPROM of the processor.

[rwyoung]

If the PIC has built-in EEPROM use the functions supplied by CCS.

Search the CCS help file for:

write_eeprom

and

read_eeprom

Also read the datasheet for your PIC very carefully reguarding the use of its internal EEPROM.
_________________
Rob Young
The Screw-Up Fairy may just visit you but he has crashed on my couch for the last month!