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Hello, I have a working LPC1758 MDK-arm 4 program that is based on the HID example.
When I set the systick to 1ms or less USB enumination fails. At 10ms all is fine, I need 1 ms for other a2d tasks.
Any ideas?
Do your other tasks take >1ms, are you spinning in loops?
What speed is the processor running?
The Cortex-M3/4 will starve foreground tasks if an interrupt pends before an IRQ Handler completes, it will just tail-chain into the next handler.
Check what pre-emption state/mode you have in the NVIC, and then what you have set for the IRQ and system handlers. Make sure the SysTick has the lowest priority.
Thanks - I will check.
LPC1758 is running 100MHz No Task takes longer than 1ms Preempion is at 50mS (round robin)
Very strange that if I set systick to 1.02mS then it works. My USB binterval is 2mS
I would suggest you try MDK 5 and latest middleware if possible.
I see this example did not use the RTOS C:\Keil_v5\ARM\Boards\Keil\MCB1700\RL\USB\Device\HID\
But if you are adjust hte systick it sounds like you may be.
If you adjust the Systick time, are you also modifying the Timer tick value [us] in the RTX_conf_CM.c
http://www.keil.com/support/man/docs/rlarm/rlarm_ar_cfgtimer.htm
Did you check the PLL, USB clock configuration settings in the system_LPC17xx.c file? Especially USBCLKCFG_Val?
Double check all clock settings - timing is critical in USB applications.
also, when debugging your application , make sure to check the Peripherals -> System Viewer -> USB window to see the USB register values.
You can adjust the systick while running your code using the Peripherals -> Core Peripherals-> Systick timer.
That way you don't have to recompile your project every time while fiddling with timings.
Thank you for your help. It looks as if tasks were "nose to tailing" and the usb was not getting in Increasing the systick by 5% fixed it