SPI Interface

[balamagesh]

I am using 16F73 with digital pot(MCP41050) and trying to control digital pot through SPI interface. The below is code used by me. Can anybody help me with modified sample code to make it work. pin RC3 -> SCK , pin RC4 -> SI , pin RB0 -> CS.

The code is as follows:

setup_spi(SPI_MASTER|SPI_H_TO_L|SPI_CLK_DIV_16);
output_high(PIN_B0);
spi_write(3);
spi_write(0x00);
output_low(PIN_B0);

Thanks in Advance
Balamgesh
___________________________
This message was ported from CCS's old forum
Original Post ID: 11585

[dave.t]

:=I am using 16F73 with digital pot(MCP41050) and trying to control digital pot through SPI interface. The below is code used by me. Can anybody help me with modified sample code to make it work. pin RC3 -> SCK , pin RC4 -> SI , pin RB0 -> CS.
:=
:=The code is as follows:
:=
:= setup_spi(SPI_MASTER|SPI_H_TO_L|SPI_CLK_DIV_16);
:= output_high(PIN_B0);
:= spi_write(3);
:= spi_write(0x00);
:= output_low(PIN_B0);
:=
:=Thanks in Advance
:=Balamgesh


Here is some code I have recently used and works fine-

void digi_pot(char data);

void digi_pot()

{

char count,command,pot_data;

pot_data=data;
command=digi_command; // 0x11

#asm
bcf clock // make sure clock is low
movlw 0x08 // load
movwf count // first 8 bit count
bcf chip_select // select chip

cmlp:bcf serial_out // data line low
rlf command,f // move command out to carry msb first
btfsc carry
bsf serial_out // data out high
nop // allow data
nop // to settle
bsf clock // clock high
nop // wait
nop // wait
bcf clock // clock low
nop
decfsz count,f // all bits clocked out?
goto cmlp
// yes!
movlw 0x08 // load
movwf count // second 8 bit count

dblp:bcf serial_out
rlf pot_data,f // pot value
btfsc carry
bsf serial_out // data output high
nop // allow data
nop // to settle
bsf clock // clock high
nop // wait
nop // wait
bcf clock // clock low
nop
decfsz count,f // all bits clocked out?
goto dblp
bsf chip_select // yes! all sixteen bits clocked out
// chip select is now taken high to latch data and update pot!
#endasm

}

Regards
Dave T.
___________________________
This message was ported from CCS's old forum
Original Post ID: 11586

[R.J.Hamlett]

:=I am using 16F73 with digital pot(MCP41050) and trying to control digital pot through SPI interface. The below is code used by me. Can anybody help me with modified sample code to make it work. pin RC3 -> SCK , pin RC4 -> SI , pin RB0 -> CS.
:=
:=The code is as follows:
:=
:= setup_spi(SPI_MASTER|SPI_H_TO_L|SPI_CLK_DIV_16);
:= output_high(PIN_B0);
:= spi_write(3);
The command format for the chip, is that the first byte contains the command data, in the form:
xxccxxpp (in binary)
You are sending a command (cc bits) of '00', which is a 'no action' command. To address both potentiometers, needs a first byte of:
xx01xx11
So try:
spi_write(0x13);

:= spi_write(0x00);
Presumably you are trying to set the pots to zero?. If so this is OK.

:= output_low(PIN_B0);
:=
:=Thanks in Advance
:=Balamgesh

Best Wishes
___________________________
This message was ported from CCS's old forum
Original Post ID: 11587

[Bruce R. Knox]

:=I am using 16F73 with digital pot(MCP41050) and trying to control digital pot through SPI interface. The below is code used by me. Can anybody help me with modified sample code to make it work. pin RC3 -> SCK , pin RC4 -> SI , pin RB0 -> CS.
:=
:=The code is as follows:
:=
:= setup_spi(SPI_MASTER|SPI_H_TO_L|SPI_CLK_DIV_16);
:= output_high(PIN_B0);
:= spi_write(3);
:= spi_write(0x00);
:= output_low(PIN_B0);
:=
:=Thanks in Advance
:=Balamgesh

The chip select is active LOW - so use output_low(PIN_B0) to select it and output_high(PIN_B0) to de-select it. Also,
make sure you set B0 high when you initialize the i/o port at the beginning of your program.

As someone else said - the first byte you send should be 0x13 to set both pots (0x11 for Pot 0 || 0x12 for Pot 1).

Then it should work.

Bruce
___________________________
This message was ported from CCS's old forum
Original Post ID: 11599

[Balamagesh]

:=:=I am using 16F73 with digital pot(MCP41050) and trying to control digital pot through SPI interface. The below is code used by me. Can anybody help me with modified sample code to make it work. pin RC3 -> SCK , pin RC4 -> SI , pin RB0 -> CS.
:=:=
:=:=The code is as follows:
:=:=
:=:= setup_spi(SPI_MASTER|SPI_H_TO_L|SPI_CLK_DIV_16);
:=:= output_high(PIN_B0);
:=:= spi_write(3);
:=The command format for the chip, is that the first byte contains the command data, in the form:
:=xxccxxpp (in binary)
:=You are sending a command (cc bits) of '00', which is a 'no action' command. To address both potentiometers, needs a first byte of:
:=xx01xx11
:=So try:
:=spi_write(0x13);
:=
:=:= spi_write(0x00);
:=Presumably you are trying to set the pots to zero?. If so this is OK.
:=
:=:= output_low(PIN_B0);
:=:=
:=:=Thanks in Advance
:=:=Balamgesh
:=
:=Best Wishes

Thanks .The below code didnt work for me. should there be any delay in between (or) the data should be spi_write(0x13ff).
Pls help me in this

setup_spi(SPI_MASTER | SPI_H_TO_L | SPI_CLK_DIV_16);
output_low(PIN_B0);
spi_write(0x13);
spi_write(0xff); //setting pot to high
output_high(PIN_B0);

Thanks
Bala
___________________________
This message was ported from CCS's old forum
Original Post ID: 12076