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alyeomans
Joined: 26 Feb 2014
Posts: 24
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| PIC18F4620 + 32kHz and sleep |
 Posted: Fri May 06, 2016 6:29 am |
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Hi All
I am looking to rewrite the firmware of a battery powered data logger. It runs a PIC18F4620 using the internal osc at 8MHz - it also has a 32kHz watch crystal used to track time for wake and sample.
Compiler 5.048
I have been reading around and have the following understanding:
1. usual setup and fuses
2. timer1 setup as secondary oscillator at @ 32 kHz
3. I need to enter SEC_IDLE mode
4. At each timer1 overflow the interrupt adds a tick or commences Run mode.
Do I need to add fuse NOLPT1OSC for no low power t1 osc?
How do you transition between different run modes in CCS -bit set or is there a function?
As the sample rate can vary from 60 sec to days is the interrupt method the only way?
As this is just outside my current realm I am looking for some good pointers to get me on the way.
Cheers
Al
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Fri May 06, 2016 8:22 am |
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| alyeomans wrote: | 3. I need to enter SEC_IDLE mode
How do you transition between different run modes in CCS -bit set or is there a function? |
The 18F4620 data sheet says:
| Quote: | 3.4.2 SEC_IDLE MODE
This mode is entered from SEC_RUN by setting
the IDLEN bit and executing a SLEEP instruction.
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Compiling the test program show below with CCS vs. 5.056 gives the
following .LST file code:
| Code: | .................... sleep(SLEEP_IDLE);
0002C: MOVFF OSCCON,00
00030: MOVLW FC
00032: ANDWF OSCCON,F
00034: BSF OSCCON.IDLEN
00036: SLEEP
00038: MOVFF 00,OSCCON |
The compiler sets the bit.
Test program:
| Quote: | #include <18F4620.h>
#fuses INTRC_IO, NOWDT
#use delay(clock=4M)
#use rs232(baud=9600, UART1, ERRORS)
//=====================================
void main()
{
sleep(SLEEP_IDLE);
while(TRUE);
} |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Re: PIC18F4620 + 32kHz and sleep |
| Posted: Fri May 06, 2016 4:04 pm |
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| alyeomans wrote: |
Do I need to add fuse NOLPT1OSC for no low power t1 osc?
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It's optional.
The 18F4620 data sheet says:
| Quote: | 12.3.2 LOW-POWER TIMER1 OPTION
The Timer1 oscillator can operate at two distinct levels
of power consumption based on device configuration.
When the LPT1OSC Configuration bit is set, the Timer1
oscillator operates in a low-power mode. When
LPT1OSC is not set, Timer1 operates at a higher power
level. Power consumption for a particular mode is
relatively constant, regardless of the device’s operating
mode. The default Timer1 configuration is the higher
power mode.
As the low-power Timer1 mode tends to be more
sensitive to interference, high noise environments may
cause some oscillator instability. The low-power option is,
therefore, best suited for low noise applications where
power conservation is an important design consideration.
|
Graph for low power mode:
| Quote: | | FIGURE 27-4: TYPICAL T1OSC DELTA CURRENT vs. VDD ACROSS TEMP. (DEVICE IN SLEEP, T1OSC IN LOW-POWER MODE) |
Graph for high power mode:
| Quote: | | FIGURE 27-6: TYPICAL T1OSC DELTA CURRENT vs. VDD ACROSS TEMP. (DEVICE IN SLEEP, T1OSC IN HIGH-POWER MODE) |
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alyeomans
Joined: 26 Feb 2014
Posts: 24
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| Posted: Fri May 06, 2016 4:57 pm |
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Thank you PCMProgrammer. I was a little lost before and your guidance is appreciated. I feel i am ready to start experimenting.
The device will be in a shielded case so I will test for the low power stability first.
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