Teensy 4.x Battery backed Non volitile memory

Mupeg · Jun 9, 2021

Howdy, all! This is as much of a check your work post as any. I was reading a previous post: https://forum.pjrc.com/threads/45854-Battery-backed-NV-RAM
regarding using the extra 28 free bytes of the 32 bytes of non-volatile battery-backed memory for run data I would like to keep after a restart.
I would like to implement a solution like this on the 4.x boards but looking at the memory map at: https://www.pjrc.com/teensy/IMXRT1060RM_rev2.pdf page: 1242 it appears that the battery-backed memory only allows for 4 bytes starting at address 0x400D4100. Firstly, am I even reading this correctly or even looking at the correct section of memory? I could not find in the teensy 4core where the RTC is even storing the time. I'm a little out of my pay grade here but trying to fake it as best I can.

Aside: This data I wish to keep is only 12 bytes but is very volatile so EPROM isn't really suitable.

defragster · Jun 9, 2021

There is NVRAM on the 1062 in the T_4.x's. There are 4 32 bit words.

Below is code that shows it in use from Feb 2021 - discussed in a post somewhere ...
> It did some things to show function including a 'r' Reset that picks up with the values intact.
> Added a 't' command it seems that isn't in the startup printing: Looks to give some idea of the timing of doing multiple writes

Key thing was finding this :: SNVS_LPCR |= (1 << 24); //Enable NVRAM - documented in SDK
Frank B found that poking bits that were not documented in the manual IIRC.

Code:

// TWO ways to access as 4 32 bit DWORDS of NVRAM backed data
// #define NVRAM_UINT32 ((uint32_t *)0x400D4100)
uint32_t *NVRAM_UINT32 ((uint32_t *)0x400D4100);
uint32_t tRam[4];

elapsedMillis tSome;
void setup() {
	[B]SNVS_LPCR |= (1 << 24); //Enable NVRAM - documented in SDK[/B]
	Serial.begin(115200);
	while (!Serial && millis() < 4000 );
	Serial.println("\n" __FILE__ " " __DATE__ " " __TIME__);
	tSome = 0;
	Serial.print(" 'r':RESTART 'z':ZERO '?':INC 100 to each\n");
	for ( int ii = 0; ii < 4; ii++ ) {
		tRam[ii] = 0;
	}
}

#define SNVS_LPGPR0      (IMXRT_SNVS.offset100)
#define SNVS_LPGPR1      (IMXRT_SNVS.offset104)
#define SNVS_LPGPR2      (IMXRT_SNVS.offset108)
#define SNVS_LPGPR3      (IMXRT_SNVS.offset10C)

void loop() {
	if ( tSome >= 1000 ) {
		tSome -= 1000;
		for ( int ii = 0; ii < 4; ii++ ) {
			Serial.print( '\t' );
			Serial.print( NVRAM_UINT32[ii] );
		}
		Serial.println();
		for ( int ii = 0; ii < 4; ii++ ) {
			NVRAM_UINT32[ii]++;
		}
	}
	while ( Serial.available() ) {
		char cc = Serial.read();
		if ( 'r' == cc ) {
			SCB_AIRCR = 0x5FA0004;
			while (true);
		}
		else if ( 'z' == cc ) {
			Serial.print( "_ZERO_ NVRAM\n" );
			for ( int ii = 0; ii < 4; ii++ ) {
				NVRAM_UINT32[ii] = ii * 1000;
			}
		}
		else if ( 't' == cc ) {
			Serial.print( "_Add_1K_ NVRAM\n" );
			uint32_t tt = micros();
			for ( int jj = 0; jj < 1000; jj++ ) {
				for ( int ii = 0; ii < 4; ii++ ) {
					NVRAM_UINT32[ii]++;
				}
			}
			tt = micros() - tt;
			Serial.printf("\t%lu us\t for 1K increments of 4 RTC DWORDS\n", tt );

			tt = micros();
			for ( int jj = 0; jj < 1000; jj++ ) {
				SNVS_LPGPR0 += 1;
				SNVS_LPGPR1 += 2;
				SNVS_LPGPR2 += 3;
				SNVS_LPGPR3 += 4;
			}
			tt = micros() - tt;
			Serial.printf("\t%lu us\t for 1K increments of 4 RTC #define DWORDS\n", tt );

			tt = micros();
			for ( int jj = 0; jj < 1000; jj++ ) {
				for ( int ii = 0; ii < 4; ii++ ) {
					tRam[ii]++;
				}
			}
			tt = micros() - tt;
			Serial.printf("\t%lu us\t\t for 1K increments of 4 RAM DWORDS\n", tt );
		}
		else {
			Serial.print( "_10_INC_ NVRAM\n" );
			tSome += 10000;
		}
	}
}

Mupeg · Jun 9, 2021

This is great! Sorry for the redundancy if I missed a previous post. I will experiment with your code this evening. Cheers!

defragster · Jun 9, 2021

Mupeg said:
This is great! Sorry for the redundancy if I missed a previous post. I will experiment with your code this evening. Cheers!

Hope it helps - post didn't pop up for me either so resorted to finding the sample sketch. One sketch does link to April 2019 - but that was before the Enable was found to make it usable.

Mupeg · Jun 10, 2021

defragster said:
Hope it helps - post didn't pop up for me either so resorted to finding the sample sketch. One sketch does link to April 2019 - but that was before the Enable was found to make it usable.

I tested out your code and it works brilliantly! I'm pretty pleased I was on the right track finding the starting address for the general-purpose registers but I doubt I would have ever found the secret sauce of the enable code. Or even realized I needed to enable it for that matter.
Thank you kindly, defragster and Frank B!

defragster · Jun 10, 2021

Awesome. It is cool to have those 4 dwords on hand to track and save EEPROM and have safe workspace. They do take measurable time to write as they pass through the low speed barrier to the other half of the chip.

defragster · Jun 16, 2021

Not that anyone asked - but for another purpose - the post#2 code for T_4.x NVRAM was updated to do the same for T_3.x's.

Tested this to work on :: T_4.1 and T_3.6 and T_3.0 { should work on anything but a T_LC }::

Code:

// TWO ways to access as 4 32 bit DWORDS of NVRAM backed data
// For T_3.x :: https://forum.pjrc.com/threads/45854-Battery-backed-NV-RAM
// #define NVRAM_UINT32 ((uint32_t *)0x400D4100)

#if defined(__IMXRT1062__)
uint32_t *NVRAM_UINT32 ((uint32_t *)0x400D4100);
#define DWORDS 4
#else
uint32_t *NVRAM_UINT32 ((uint32_t *)0x4003E000);
#define DWORDS 7
#endif

uint32_t tRam[DWORDS]; // just for speed compare of writes

elapsedMillis tSome;
void setup() {
#if defined(__IMXRT1062__)
	SNVS_LPCR |= (1 << 24); //Enable NVRAM - documented in SDK
#endif
	Serial.begin(115200);
	while (!Serial && millis() < 4000 );
	Serial.println("\n" __FILE__ " " __DATE__ " " __TIME__);
	tSome = 0;
	showHelp();
	for ( int ii = 0; ii < DWORDS; ii++ ) {
		tRam[ii] = 0;
	}
}

void loop() {
	if ( tSome >= 1000 ) {
		tSome -= 1000;
		for ( int ii = 0; ii < DWORDS; ii++ ) {
			Serial.print( '\t' );
			Serial.print( NVRAM_UINT32[ii] );
		}
		Serial.println();
		for ( int ii = 0; ii < DWORDS; ii++ ) {
			NVRAM_UINT32[ii]++;
		}
	}
	while ( Serial.available() ) {
		char cc = Serial.read();
		if ( 'r' == cc ) {
			SCB_AIRCR = 0x5FA0004;
			while (true);
		}
		else if ( 'z' == cc ) {
			Serial.print( "_ZERO_ NVRAM\n" );
			for ( int ii = 0; ii < DWORDS; ii++ ) {
				NVRAM_UINT32[ii] = ii * 1000;
			}
		}
		else if ( 't' == cc ) {
			Serial.print( "_Add_1K_ NVRAM\n" );
			uint32_t tt = micros();
			for ( int jj = 0; jj < 1000; jj++ ) {
				for ( int ii = 0; ii < DWORDS; ii++ ) {
					NVRAM_UINT32[ii]++;
				}
			}
			tt = micros() - tt;
			Serial.printf("\t%lu us\t for 1K increments of 4 (7) RTC DWORDS\n", tt );
			tt = micros();
#if defined(__IMXRT1062__)
			for ( int jj = 0; jj < 1000; jj++ ) {
				SNVS_LPGPR0 += 1;
				SNVS_LPGPR1 += 2;
				SNVS_LPGPR2 += 3;
				SNVS_LPGPR3 += 4;
			}
#else
			for ( int jj = 0; jj < 1000; jj++ ) {
				for ( int ii = 0; ii < DWORDS; ii++ ) {
					NVRAM_UINT32[ii] += 1+ii ;
				}
			}
#endif

			tt = micros() - tt;
			Serial.printf("\t%lu us\t for 1K increments of 4 (7) RTC #define DWORDS\n", tt );

			tt = micros();
			for ( int jj = 0; jj < 1000; jj++ ) {
				for ( int ii = 0; ii < DWORDS; ii++ ) {
					tRam[ii]++;
				}
			}
			tt = micros() - tt;
			Serial.printf("\t%lu us\t\t for 1K increments of 4 (7) RAM DWORDS\n", tt );
		}
		else if ( '?' == cc ) {
			showHelp();
		}
		else {
			Serial.print( "_10_INC_ NVRAM\n" );
			tSome += 10000;
		}
	}
}

void showHelp() {
	Serial.print(" 'r':RESTART 'z':ZERO '?':Help t:INC 1K else:INC 10 to each\n");
}

bicycleguy · Jul 6, 2021

@defragster
Copied the sketch above (#7) and it seems to work fine on a battery backed T3.2 when running or reprogramming it starts where it left off. But when I unplug the USB and replug it starts with 0s. The battery is good as the RTC is running on this board.

Any ideas?

defragster · Jul 6, 2021

bicycleguy said:
@defragster
Copied the sketch above (#7) and it seems to work fine on a battery backed T3.2 when running or reprogramming it starts where it left off. But when I unplug the USB and replug it starts with 0s. The battery is good as the RTC is running on this board.

Any ideas?

I'd have to try it, those values were understood to be battery backed.

Was RTC cell proper polarity and well connected?

defragster · Jul 6, 2021

T_3.2 working here ... had to solder a battery.

> Confirm good cell near 3V
> + on vBat
> - on GND
> Crystal soldered to T_3.2

Run Sketch p#7 - edited below to show TIME HH : MM : SS

>> Restart Teensy with 'r'
>> Unpower T_3.2 on hub switch
>> Unplug T_3.2

On restart all three of those show count continuing
Did a quick mod with code from earlier today to show the TIME - unplugged over 30 seconds and all is well:

Code:

T:\tCode\NVRAM_T\NVRAM_3_4\NVRAM_3_4.ino Jul  6 2021 19:21:41
RTC has set system time
[B][COLOR="#FF0000"]hour:19	minute:22	second:16[/COLOR][/B]
 'r':RESTART 'z':ZERO '?':Help t:INC 1K else:INC 10 to each
	2611	3611	4611	5611	6611	7611	8611
	2612	3612	4612	5612	6612	7612	8612
	2613	3613	4613	5613	6613	7613	8613
	2614	3614	4614	5614	6614	7614	8614
T:\tCode\NVRAM_T\NVRAM_3_4\NVRAM_3_4.ino Jul  6 2021 19:21:41
RTC has set system time
[B][COLOR="#FF0000"]hour:19	minute:22	second:57[/COLOR][/B]
 'r':RESTART 'z':ZERO '?':Help t:INC 1K else:INC 10 to each
	2615	3615	4615	5615	6615	7615	8615
	2616	3616	4616	5616	6616	7616	8616

New code to confirm RTC is up and running:

Code:

// TWO ways to access as 4 32 bit DWORDS of NVRAM backed data
// For T_3.x :: https://forum.pjrc.com/threads/45854-Battery-backed-NV-RAM
// #define NVRAM_UINT32 ((uint32_t *)0x400D4100)

#include <TimeLib.h>
#if defined(__IMXRT1062__)
uint32_t *NVRAM_UINT32 ((uint32_t *)0x400D4100);
#define DWORDS 4
#else
uint32_t *NVRAM_UINT32 ((uint32_t *)0x4003E000);
#define DWORDS 7
#endif

uint32_t tRam[DWORDS]; // just for speed compare of writes

elapsedMillis tSome;

void showTime(void)
{
	setSyncProvider(getTeensy3Time);                                // use the Teensy 4.0 RTC timer

	if (timeStatus() != timeSet)
		Serial.println(F("Unable to sync with RTC"));
	else
		Serial.println(F("RTC has set system time"));

	time_t tm = Teensy3Clock.get();
	tm = now();
	Teensy3Clock.set(tm);
	Serial.print("hour:");
	Serial.print(hour());
	Serial.print("\tminute:");
	Serial.print(minute());
	Serial.print("\tsecond:");
	Serial.println(second());
}


void setup() {
#if defined(__IMXRT1062__)
	SNVS_LPCR |= (1 << 24); //Enable NVRAM - documented in SDK
#endif
	Serial.begin(115200);
	while (!Serial && millis() < 4000 );
	Serial.println("\n" __FILE__ " " __DATE__ " " __TIME__);
	tSome = 0;
	showTime();
	showHelp();
	for ( int ii = 0; ii < DWORDS; ii++ ) {
		tRam[ii] = 0;
	}
}

void loop() {
	if ( tSome >= 1000 ) {
		tSome -= 1000;
		for ( int ii = 0; ii < DWORDS; ii++ ) {
			Serial.print( '\t' );
			Serial.print( NVRAM_UINT32[ii] );
		}
		Serial.println();
		for ( int ii = 0; ii < DWORDS; ii++ ) {
			NVRAM_UINT32[ii]++;
		}
	}
	while ( Serial.available() ) {
		char cc = Serial.read();
		if ( 'r' == cc ) {
			SCB_AIRCR = 0x5FA0004;
			while (true);
		}
		else if ( 'z' == cc ) {
			Serial.print( "_ZERO_ NVRAM\n" );
			for ( int ii = 0; ii < DWORDS; ii++ ) {
				NVRAM_UINT32[ii] = ii * 1000;
			}
		}
		else if ( 't' == cc ) {
			Serial.print( "_Add_1K_ NVRAM\n" );
			uint32_t tt = micros();
			for ( int jj = 0; jj < 1000; jj++ ) {
				for ( int ii = 0; ii < DWORDS; ii++ ) {
					NVRAM_UINT32[ii]++;
				}
			}
			tt = micros() - tt;
			Serial.printf("\t%lu us\t for 1K increments of 4 (7) RTC DWORDS\n", tt );
			tt = micros();
#if defined(__IMXRT1062__)
			for ( int jj = 0; jj < 1000; jj++ ) {
				SNVS_LPGPR0 += 1;
				SNVS_LPGPR1 += 2;
				SNVS_LPGPR2 += 3;
				SNVS_LPGPR3 += 4;
			}
#else
			for ( int jj = 0; jj < 1000; jj++ ) {
				for ( int ii = 0; ii < DWORDS; ii++ ) {
					NVRAM_UINT32[ii] += 1 + ii ;
				}
			}
#endif

			tt = micros() - tt;
			Serial.printf("\t%lu us\t for 1K increments of 4 (7) RTC #define DWORDS\n", tt );

			tt = micros();
			for ( int jj = 0; jj < 1000; jj++ ) {
				for ( int ii = 0; ii < DWORDS; ii++ ) {
					tRam[ii]++;
				}
			}
			tt = micros() - tt;
			Serial.printf("\t%lu us\t\t for 1K increments of 4 (7) RAM DWORDS\n", tt );
		}
		else if ( '?' == cc ) {
			showHelp();
		}
		else {
			Serial.print( "_10_INC_ NVRAM\n" );
			tSome += 10000;
		}
	}
}

void showHelp() {
	Serial.print(" 'r':RESTART 'z':ZERO '?':Help t:INC 1K else:INC 10 to each\n");
}

time_t getTeensy3Time()
{
	return Teensy3Clock.get();
}

bicycleguy · Jul 6, 2021

After posting, over dinner it dawned on me that maybe the battery was bad and sure enough checking, it is 1.22V. Apparently this is enough to keep the RTC going accurately but not enough for the NVRAM !
A fresh battery fixed the problem. Maybe I'll see how low it can go.

thanks

bicycleguy · Jul 6, 2021

see you posted some more info,

thanks

defragster · Jul 6, 2021

bicycleguy said:
After posting, over dinner it dawned on me that maybe the battery was bad and sure enough checking, it is 1.22V. Apparently this is enough to keep the RTC going accurately but not enough for the NVRAM !
A fresh battery fixed the problem. Maybe I'll see how low it can go.

thanks

Glad it is working! After soldering had to use DMM to confirm 2032 here was good ...

RTC will get set on restart to COMPILE TIME if found unset.

Not sure how the RTC running was confirmed?

The Date and Time printed in setup() is time of compile as well - no RTC ref in that.

bicycleguy · Jul 6, 2021

I can't be sure the clock was running because I didn't check the time and re-programming resets a dead clock as you know. I'll reload the original program and see if and how long the clock keeps running on the old battery.

If there is a difference in the voltage between when the clock dies and when the memory doesn't stick I could build in a feature to check a NVRAM variable agains a EEPROM variable or may just zero to determine when the clock battery needs replaced without actually measuring it!

defragster · Jul 6, 2021

Reprogramming provides a NEW time - stored in the sketch at the time of the build.

As noted on each restart when the RTC memory is seen as 'unset' - it uses the 8th DWORD maintained by T_3.x's after those 7 shown above to determine that IIRC.

When it is seen as unset - it put the time of last compile as stored in the sketch.

So when using the low V battery - check the time shown against a running clock. On each repower it may come up running the time of last build.

bicycleguy · Jul 6, 2021

You are correct, whether the RTC was running or not, can't tell because as you said it uses the cleared memory to reset the clock. On mine its at about 1.238V that it dies. Oh well, fun thought.

defragster · Jul 7, 2021

bicycleguy said:
You are correct, whether the RTC was running or not, can't tell because as you said it uses the cleared memory to reset the clock. On mine its at about 1.238V that it dies. Oh well, fun thought.

Hard to see how the RTC could be active when it isn't keeping 'static' memory. Paul must have looked into that as the key to overwrite the Build time into the RTC on startp

defragster · Nov 1, 2022

Posting code as found locally - as it has some minor diff?

Code:

// Accessing as 4 32 bit DWORDS of NVRAM backed data on 1062 MCU
// For T_3.x there are 7 DWORDS, the 8th is used by PJRC to track valid RTC clock

#include <TimeLib.h>
#if defined(__IMXRT1062__)
uint32_t *NVRAM_UINT32 ((uint32_t *)0x400D4100);
//uint32_t *NVRAM_UINT32 (SNVS_LPGPR0);
#define DWORDS 4
#else
uint32_t *NVRAM_UINT32 ((uint32_t *)0x4003E000);
#define DWORDS 7
#endif

uint32_t tRam[DWORDS]; // just for speed compare of writes

elapsedMillis tSome;

void showTime(void)
{
	setSyncProvider(getTeensy3Time);                                // use the Teensy 4.0 RTC timer

	if (timeStatus() != timeSet)
		Serial.println(F("Unable to sync with RTC"));
	else
		Serial.println(F("RTC has set system time"));

	time_t tm = Teensy3Clock.get();
	tm = now();
	Teensy3Clock.set(tm);
	Serial.print("hour:");
	Serial.print(hour());
	Serial.print("\tminute:");
	Serial.print(minute());
	Serial.print("\tsecond:");
	Serial.println(second());
}


void setup() {
#if defined(__IMXRT1062__)
	SNVS_LPCR |= (1 << 24); //Enable NVRAM - documented in SDK
#endif
	Serial.begin(115200);
	while (!Serial && millis() < 4000 );
	if ( CrashReport ) Serial.print( CrashReport );
	Serial.println("\n" __FILE__ " " __DATE__ " " __TIME__);
	tSome = 0;
	showTime();
	showHelp();
	for ( int ii = 0; ii < DWORDS; ii++ ) {
		tRam[ii] = 0;
	}
}

void loop() {
	if ( tSome >= 1000 ) {
		tSome -= 1000;
		for ( int ii = 0; ii < DWORDS; ii++ ) {
			Serial.print( '\t' );
			Serial.print( NVRAM_UINT32[ii] );
		}
		Serial.println();
		for ( int ii = 0; ii < DWORDS; ii++ ) {
			NVRAM_UINT32[ii]++;
		}
	}
	while ( Serial.available() ) {
		char cc = Serial.read();
		if ( 'r' == cc ) {
			SCB_AIRCR = 0x5FA0004;
			while (true);
		}
		else if ( 'b' == cc ) {
			Serial.print( "Bootloader !!!\n" );
			delay(10);
			asm("bkpt #251");
		}
		else if ( 'z' == cc ) {
			Serial.print( "_ZERO_ NVRAM\n" );
			for ( int ii = 0; ii < DWORDS; ii++ ) {
				NVRAM_UINT32[ii] = 0;
			}
		}
		else if ( 't' == cc ) {
			Serial.print( "_Add_1K_ NVRAM\n" );
			NVRAM_UINT32[0] = NVRAM_UINT32[1] = NVRAM_UINT32[2] = NVRAM_UINT32[3]=0;
			uint32_t tt = micros();
			for ( int jj = 0; jj < 1000; jj++ ) {
#if 1
					NVRAM_UINT32[0]+=1;
					NVRAM_UINT32[1]+=2;
					NVRAM_UINT32[2]+=3;
					NVRAM_UINT32[3]+=4;
#else
				for ( int ii = 0; ii < DWORDS; ii++ ) {
					NVRAM_UINT32[ii]++;
				}
#endif
			}
			tt = micros() - tt;
			Serial.printf("\t%lu us\t for 1K increments of 4 (7) RTC DWORDS\n", tt );
			Serial.printf("\tvals= %lu %lu %lu %lu \n", NVRAM_UINT32[0], NVRAM_UINT32[1], NVRAM_UINT32[2], NVRAM_UINT32[3] );
			NVRAM_UINT32[0] = NVRAM_UINT32[1] = NVRAM_UINT32[2] = NVRAM_UINT32[3]=0;
			tt = micros();
#if defined(__IMXRT1062__)
			for ( int jj = 0; jj < 1000; jj++ ) {
				SNVS_LPGPR0 += 1;
				SNVS_LPGPR1 += 2;
				SNVS_LPGPR2 += 3;
				SNVS_LPGPR3 += 4;
			}
#else
			for ( int jj = 0; jj < 1000; jj++ ) {
				for ( int ii = 0; ii < DWORDS; ii++ ) {
					NVRAM_UINT32[ii] += 1 + ii ;
				}
			}
#endif

			tt = micros() - tt;
			Serial.printf("\t%lu us\t for 1K increments of 4 (7) RTC #define DWORDS\n", tt );
			Serial.printf("\tvals= %lu %lu %lu %lu \n", NVRAM_UINT32[0], NVRAM_UINT32[1], NVRAM_UINT32[2], NVRAM_UINT32[3] );

			tt = micros();
			for ( int jj = 0; jj < 1000; jj++ ) {
				CrashReport.breadcrumb( 1, jj );
				CrashReport.breadcrumb( 2, jj );
				CrashReport.breadcrumb( 3, jj );
				CrashReport.breadcrumb( 4, jj );
			}

			tt = micros() - tt;
			Serial.printf("\t%lu us\t for 1K increments of breadcrumb DWORDS\n", tt );

			Serial.print( "_Add_1K_ NVRAM\n" );
			NVRAM_UINT32[0] = NVRAM_UINT32[1] = NVRAM_UINT32[2] = NVRAM_UINT32[3]=0;
			tt = micros();
			for ( int jj = 0; jj < 1000; jj++ ) {
#if 1
					NVRAM_UINT32[0]=jj;
					NVRAM_UINT32[1]=jj;
					NVRAM_UINT32[2]=jj;
					NVRAM_UINT32[3]=jj;
#else
				for ( int ii = 0; ii < DWORDS; ii++ ) {
					NVRAM_UINT32[ii]++;
				}
#endif
			}
			tt = micros() - tt;
			Serial.printf("\t%lu us\t for 1K increments of 4 (7) RTC DWORDS\n", tt );
			Serial.printf("\tvals= %lu %lu %lu %lu \n", NVRAM_UINT32[0], NVRAM_UINT32[1], NVRAM_UINT32[2], NVRAM_UINT32[3] );
			NVRAM_UINT32[0] = NVRAM_UINT32[1] = NVRAM_UINT32[2] = NVRAM_UINT32[3]=0;
			tt = micros();
#if defined(__IMXRT1062__)
			for ( int jj = 0; jj < 1000; jj++ ) {
				SNVS_LPGPR0 =jj;
				SNVS_LPGPR1 =jj;
				SNVS_LPGPR2 =jj;
				SNVS_LPGPR3 =jj;
			}
#else
			for ( int jj = 0; jj < 1000; jj++ ) {
				for ( int ii = 0; ii < DWORDS; ii++ ) {
					NVRAM_UINT32[ii] += 1 + ii ;
				}
			}
#endif
			tt = micros() - tt;
			Serial.printf("\t%lu us\t for 1K increments of 4 (7) RTC #define DWORDS\n", tt );
			Serial.printf("\tvals= %lu %lu %lu %lu \n", NVRAM_UINT32[0], NVRAM_UINT32[1], NVRAM_UINT32[2], NVRAM_UINT32[3] );

			tt = micros();
			for ( int jj = 0; jj < 1000; jj++ ) {
				CrashReport.breadcrumb( 1, jj );
				CrashReport.breadcrumb( 2, jj );
				CrashReport.breadcrumb( 3, jj );
				CrashReport.breadcrumb( 4, jj );
			}

			tt = micros() - tt;
			Serial.printf("\t%lu us\t for 1K increments of breadcrumb DWORDS\n", tt );

			tt = micros();
			for ( int jj = 0; jj < 1000; jj++ ) {
				for ( int ii = 0; ii < DWORDS; ii++ ) {
					tRam[ii]++;
				}
			}
			tt = micros() - tt;
			Serial.printf("\t%lu us\t\t for 1K increments of 4 (7) RAM DWORDS\n", tt );
		}
		else if ( '?' == cc ) {
			showHelp();
		}
		else {
			Serial.print( "_10_INC_ NVRAM\n" );
			tSome += 10000;
		}
	}
}

void showHelp() {
	Serial.print(" 'r':RESTART 'b':bootloadr 'z':ZERO '?':Help t:INC 1K else:INC 10 to each\n");
}

time_t getTeensy3Time()
{
	return Teensy3Clock.get();
}

Teensy 4.x Battery backed Non volitile memory

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