Debugging with LMIC_X_DEBUG_PRINTF()

[chocotov1]

I'm interested in some of the LMIC_X_DEBUG_PRINTF() lines that are in the code, for instance here:

arduino-lmic/src/lmic/lmic.c

Lines 1519 to 1531 in 8d378ea

	static void schedRx12 (ostime_t delay, osjobcb_t func, u1_t dr) {
	ostime_t hsym = dr2hsym(dr);
	// Schedule the start of the receive window. os_getRadioRxRampup() is used to make sure we
	// exit "sleep" well enough in advance of the receive window to be able to
	// time things accurately.
	//
	// This also sets LMIC.rxsyms. This is NOT normally used for FSK; see LMICbandplan_txDoneFSK()
	LMIC.rxtime = LMIC.txend + LMICcore_adjustForDrift(delay, hsym, LMICbandplan_MINRX_SYMS_LoRa_ClassA);
	LMIC_X_DEBUG_PRINTF("%"LMIC_PRId_ostime_t": sched Rx12 %"LMIC_PRId_ostime_t"\n", os_getTime(), LMIC.rxtime - os_getRadioRxRampup());
	os_setTimedCallback(&LMIC.osjob, LMIC.rxtime - os_getRadioRxRampup(), func);
	}

Contents of lmic_project_config.h:

#define LMIC_DEBUG_LEVEL 1
#define LMIC_PRINTF_TO Serial
#define LMIC_X_DEBUG_LEVEL 1

I'm getting this error:

 #    error "LMIC_DEBUG_PRINTF_FN must be defined for LMIC_X_DEBUG_LEVEL > 0."
      ^~~~~

I tried out a few different values for LMIC_DEBUG_PRINTF_FN, sadly without success

Can someone help me enable the LMIC_X_DEBUG_PRINTF() debug lines? I'm testing with a 328p in the Arduino IDE.

[terrillmoore]

I've only tested LMIC_X_DEBUG_PRINTF() on Arm Cortex M0 ports, and non-Arduino C ports, where it was easy enough to provide a printf()-like function. As I recall, this is not easy to do with a 328p because there is not a printf()-like function you can use. I debug LMIC changes on ARM ports so I don't have to deal with size constraints.

Remember that the debug-prints break timing. For this reason, unless you're debugging changes to the LMIC library, they're not useful-- if the LMIC's logic is correct, the only thing they'll do is break timing. Since they're focused on LMIC debugging, they generally don't give any useful info about integration problems. If you're using a release version of the LMIC and you're having problems, almost certainly it's an integration problem, or a known issue.

In my experience, for general debugging and catching what's going on, it's much more useful to enable logging, and then do something to capture and display the logs as in the compliance sketch. As long as you don't dump the log buffer while the LMIC is busy, this approach is non-intrusive.

[chocotov1]

Thanks for the quick and elaborate reply!

I'm aware that debugging over serial like this can introduce problems with the timings. Indeed the LMIC_X_DEBUG_PRINTF() lines might not be very useful, but since they're there I was interested in exposing them

I'm using MiniCore which provides printf, so this isn't a problem in my case. The normal LMIC_DEBUG_PRINTF() lines were already being printed to serial.

arduino-lmic/src/lmic/lmic.h

Lines 45 to 47 in 8d378ea

	# ifdef LMIC_DEBUG_PRINTF_FN
	extern void LMIC_DEBUG_PRINTF_FN(const char *f, ...);
	# endif // ndef LMIC_DEBUG_PRINTF_FN

Previously i've tried values like Serial or printf for LMIC_X_DEBUG_FN. I think the errors I got before were, that these things were already defined. After your tip I tried some more things and found the solution.

Working solution for me:

lmic_project_config.h:

#define LMIC_X_DEBUG_LEVEL 1
#define LMIC_DEBUG_PRINTF_FN MyDebug

Added this function definition to my sketch:

void MyDebug (const char* f, ...){
   Serial.printf(f);
}