TM4C1294NCPDT: Sleep mode while debugging

Bruno Saraiva

Part Number: TM4C1294NCPDT
Other Parts Discussed in Thread: EK-TM4C1294XL

Fellows,

We started the mission of implementing power saving to our projects, by using different sleep modes.

Because the first attempt directly at our own code failed (FaultISR), we decided to use a TM4C1294 EK Launchpad, and imported the sleep_modes Tivaware example. First attempt there also failed: after toggling the power mode a couple of times, timer-driven led ceased to blink, and code was stuck at FaultISR.

Having read something about Sleep Mode versus Debugging, we decided to run the board again without having the JTAG debugger active - in which case the code runs properly.

Is that really the reason? Maybe worth mentioning that the TivaWare tested example used compiler 5.2.6 during its creation, while I am using TI v18.1.1.LTS.

If in fact SleepMode can't be used during debugging, is there any flag/register that can be checked to verify that debug is active, so that a conditional call to SysCtlSleep() can be applied?

Regards

Bruno

over 7 years ago

0 Bob Crosby over 7 years ago

TI__Guru 72500 points

Hi Bruno,

Reading the C_DEBUGEN bit (bit 0) of the Debug Halting Control and Status Register (DHCSR, 0xE000EDF0) should tell you if a debugger is attached to the M4 processor.

Link from ARM:

https://static.docs.arm.com/ddi0403/e/DDI0403E_B_armv7m_arm.pdf#page=759

Here is a simple project I created that reads this bit. If I load and execute on the EK-TM4C1294XL launchpad, I get "The debugger is connected!" and a slow blink rate on LED1. If I then disconnect the debugger and hit the reset button, I get "The debugger is not connected!" on the terminal and a faster blink rate.

/cfs-file/__key/communityserver-discussions-components-files/908/EK_2D00_DebuggerCheck.zip

0 Bruno Saraiva over 7 years ago in reply to Bob Crosby

Guru 13040 points

Hello Bob,

Thanks a lot for the help, and sorry I did not reply before - totally overloaded around here!

Just for the record, if anyone cares to look for a different syntax, this post also refers to debugger detection:
e2e.ti.com/.../1350268

And I was able to confirm that any attempt to enter Sleep Mode while the debugger is attached causes FaultISR, hence a solution like this is almost mandatory (I actually wonder why so few forum posts on the theme).

Regards

Bruno

Arm-based microcontrollers

Arm-based microcontrollers forum

TM4C1294NCPDT: Sleep mode while debugging