Tool/software:
Hi there,
I have a system which runs off of INT_myCPUTIMER1_ISR and gets triggered every 1ms. Until now we had the system being clocked off the internal oscillators and I noticed this timer is 99.76% accurate against an RTC over time.
We have a 10 MHz external oscillator part number: SG-210STF 10.0000ML5 connected to GPIO19_X1 which I recently used for the system clock by uncommenting #define USE_PLL_SRC_XTAL and commenting #define USE_PLL_SRC_INTOSC in the device.h file.
I also changed the following code to indicate the single ended oscillator:
#define DEVICE_SETCLOCK_CFG (SYSCTL_OSCSRC_XTAL_SE | SYSCTL_IMULT(30) | \
SYSCTL_REFDIV(1) | SYSCTL_ODIV(3) | \
SYSCTL_SYSDIV(1) | SYSCTL_PLL_ENABLE | \
SYSCTL_DCC_BASE_0)
This code was previously:
#define DEVICE_SETCLOCK_CFG (SYSCTL_OSCSRC_OSC2 | SYSCTL_IMULT(30) | \
SYSCTL_REFDIV(1) | SYSCTL_ODIV(3) | \
SYSCTL_SYSDIV(1) | SYSCTL_PLL_ENABLE | \
SYSCTL_DCC_BASE_0)
Now running our code I noticed that with the NEW configuration out timer accuracy is only 99% against an RTC. This is strange because our external crystal should have an accuracy MUCH higher than this.
Do you have any idea how this could be possible? I have not modified our timer settings at all between the two configurations. Our scope of the clock signal also looks clean enough. (attached).
Thanks in advance,
Steven
