64-bit output

[todd]

Hello All,

I am trying to output 64-bits of data serially at a 2kHz rate through a single output pin. I am using the shift_left command to do this. My partial code is:

byte chan0[8] = {0xF6, 0xDB, 0x6D, 0xB7,
0xBD, 0xB7, 0xBD, 0xEF};

//// *** output here **** /////
for (n=0; n<8; n++)
{
for (m=0; m<8; m++)
{
// output MSB of byte[n]; 1-byte only; replace w/ 0
signal_temp = chan0[n];
output_bit(PIN_B0, shift_left(signal_temp, 1, 0));
delay_us(500); //sets 2kHz rate
}
}

I am not seeing anything out of PIN_B0. Through troubleshooting, I know that the routine is being called and that the for-loop is running correctly. I think that the problem is with the shift_left command (I used an example from the CCS help files, but don't have any other documentation on how this works).

Does anyone see anything wrong w/ my code? Or does anyone know a better way to output a 64-bit signal serially at a 2kHz (the order needs to be MSB -> LSB)?

Thanks in advance for anyone w/ input!
___________________________
This message was ported from CCS's old forum
Original Post ID: 4265

[Todd C. Micallef]

<font face="Courier New" size=-1>First, since you didn't list the entire program it's hard to determine the port b problem. My guess would be that you don't have the port b pull-ups enabled(if the chip supports them).
The function PORT_B_PULLUPS(TRUE); should help if this is the reason you don't see the value change.

Second look at the file "ex_sqw.c" for an example on sending data at a specific rate.


Try making these other changes...

No guarantees this is 100\% correct, but should get you in the ballpark.

:=Hello All,
:=
:=I am trying to output 64-bits of data serially at a 2kHz rate through a single output pin. I am using the shift_left command to do this. My partial code is:

byte chan0[8] = {0xF6, 0xDB, 0x6D, 0xB7,
0xBD, 0xB7, 0xBD, 0xEF};

//// *** output here **** /////
for(n=0;n<64;n++)
{
// output MSB of byte[n]; 1-byte only; replace w/ 0
output_bit(PIN_B0, shift_left(chan0, 8, 0));//8=8bytes
delay_us(250); //sets 2kHz rate
output_bit(PIN_B0,0); //If bit was high, goes to low: 50\%duty
delay_us(250);
}

:=I am not seeing anything out of PIN_B0. Through troubleshooting, I know that the routine is being called and that the for-loop is running correctly. I think that the problem is with the shift_left command (I used an example from the CCS help files, but don't have any other documentation on how this works).
:=
:=Does anyone see anything wrong w/ my code? Or does anyone know a better way to output a 64-bit signal serially at a 2kHz (the order needs to be MSB -> LSB)?
:=
:=Thanks in advance for anyone w/ input!</font>
___________________________
This message was ported from CCS's old forum
Original Post ID: 4269

[Mark]

The shift left command is used to shift bits into an array. I do not think it returns the value shifted out. If it did, I see a problem in your logic. Each time through the m for loop the signal_temp gets reassigned. It should have been outside the m loop. If I were doing this, I would do something like the following:

byte chan0[8] = {0xF6, 0xDB, 0x6D, 0xB7,
0xBD, 0xB7, 0xBD, 0xEF};

//// *** output here **** /////
for (n=0; n<8; n++)
{
signal_temp = chan0[n];
for (m=0; m<8; m++)
{
// output MSB of byte[n]
if (signal_temp & 0x80)
output_high(PIN_B0);
else
output_low(PIN_B0);
signal_temp <<= 1;
delay_us(500); //sets 2kHz rate
}
}

Depending on what you are doing, you could also use a timer int to avoid wasting CPU time.

Mark

:=Hello All,
:=
:=I am trying to output 64-bits of data serially at a 2kHz rate through a single output pin. I am using the shift_left command to do this. My partial code is:
:=
:=byte chan0[8] = {0xF6, 0xDB, 0x6D, 0xB7,
:= 0xBD, 0xB7, 0xBD, 0xEF};
:=
:=//// *** output here **** /////
:=for (n=0; n<8; n++)
:={
:= for (m=0; m<8; m++)
:= {
:= // output MSB of byte[n]; 1-byte only; replace w/ 0
:= signal_temp = chan0[n];
:= output_bit(PIN_B0, shift_left(signal_temp, 1, 0));
:= delay_us(500); //sets 2kHz rate
:= }
:=}
:=
:=I am not seeing anything out of PIN_B0. Through troubleshooting, I know that the routine is being called and that the for-loop is running correctly. I think that the problem is with the shift_left command (I used an example from the CCS help files, but don't have any other documentation on how this works).
:=
:=Does anyone see anything wrong w/ my code? Or does anyone know a better way to output a 64-bit signal serially at a 2kHz (the order needs to be MSB -> LSB)?
:=
:=Thanks in advance for anyone w/ input!
___________________________
This message was ported from CCS's old forum
Original Post ID: 4273