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sean petty
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| Varying delay longer than 255? |
 Posted: Mon Dec 30, 2002 5:46 pm |
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I am trying to create a simple LED flasher that starts slow and increments each second, from a rate of 1HZ up to a rate of 5Hz, but I'd like a small step size. Ideally I am trying to increment the rate 50ms each loop, and have it flash at that rate for 10 seconds.
More specifically,
1. Start flashing at 1 Hz (1000ms on/1000ms off) for 10 seconds, or 10000ms.
2. Increase the period by 50ms
3. Flash at the new period, 1050ms on/1050ms off) for 10 seconds.
4. Increase the period by 50ms
5. Continue...
The problem I'm having is that I'm not sure how to work around the 0-255 variable constraint. How can I get a value of 1000, 1050, 1100, etc to delay_ms in order to accomplish this?
I'm currently using 2 for loops, and using the loop counter as my variable, but obviously that doesn't work.
Can anyone suggest some code as a workaround or direct me towards a manual page or other resource that might help me find the answer?
Thanks very much.
___________________________
This message was ported from CCS's old forum
Original Post ID: 10342 |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Re: Varying delay longer than 255? |
| Posted: Mon Dec 30, 2002 6:48 pm |
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:=The problem I'm having is that I'm not sure how to work around the 0-255 variable constraint. How can I get a value of 1000, 1050, 1100, etc to delay_ms in order to accomplish this?
:=
----------------------------------------------------------
Here is a demo program. The delay function can
accept a variable with a value of 1 to 65536.
This gives a maximum delay of 65.5 seconds.
| Code: |
#include "c:\program files\picc\devices\16F877.h"
#fuses HS,NOWDT,NOPROTECT,PUT,BROWNOUT, NOLVP
#use Delay(clock=8000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
void long_delay_ms(long count);
//=============================
void main()
{
printf("Start\n\r");
long_delay_ms(30000);
printf("Done\n\r");
while(1);
}
//=============================
void long_delay_ms(long count)
{
long k;
for(k = 0; k < count; k++)
delay_ms(1);
}
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Edited to put code in a code block.
___________________________
This message was ported from CCS's old forum
Original Post ID: 10345
Last edited by PCM programmer on Sun Feb 15, 2009 12:30 pm; edited 1 time in total |
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anestho
Joined: 27 Dec 2006
Posts: 28
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| Posted: Wed Sep 19, 2007 8:48 pm |
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I tried using this routine with delay_us instead, but it doesn't work.
| Code: | void long_delay_us(long count)
{
long k;
for(k = 0; k < count; k++)
{
delay_us(1);
}
} |
Is there any other way to generate 0 to 8000 in 1us increments? I will be using a int16 as the variable. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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anestho
Joined: 27 Dec 2006
Posts: 28
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| Posted: Wed Sep 19, 2007 9:03 pm |
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I have version 3.249. I need 1 us increments or at least 4 us increments from 1000 to 2000 using a variable.
Your code for long_delay_us increments in 253 us and is used to generate delays in ms.
Any other ideas? |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Wed Sep 19, 2007 9:13 pm |
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No, that's not true. It delays in increments of 1 us.
The "253" value that you see, is actually used in a loop that delays in
increments of 256 us. This takes care of any portion of the delay that
is larger than 255 us. The CCS delay_us() routine is used for the
remainder of the delay (values of 255 us or less). The value of 253 is
used because the loop code itself takes about 3 us, at the oscillator
frequency that was used in that test program.
For people who have vs. 4.xxx of the compiler, you do not need this
routine. The delay_us() routine can handle values of up to 65535 as
either a constant or a variable parameter. |
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