![]() PinMode(outLed, OUTPUT) // set the PWM pin as OUTPUT Int value = 0 //variable to store the read value Val: int value of duty cycle between from 0(always off) to 255(always on)Įxample Code: int outLed = 10 //LED connected to digital pin 10 The analogWrite() is on a scale of 0 - 255, such that analogWrite(255) requests a 100% duty cycle (always on), and analogWrite(127) is a 50% duty cycle (on half the time). Maybe with that, a minimal example could be constructed rather than basing on the existing example, or the existing example could be further reduced?Ĭan we test this on newer gcc versions (or did we already)? It seems Arduino now ships 7.3.0, not sure if there are any versions available in staging or elsewhere? Debian only has 5.4.0 it seems.AnalogWrite(): The analogWrite() method sets the value of a PWM output pin. set the minimum number of case labels for using a jumptable to 1). One thing that could maybe help is to pass -param case-values-threshold=1 to gcc, to make it generate a jump table for all switches (i.e. Not sure if it is minimal enough yet for a gcc bugreport, I suspect that there are still some definitions and declarations that can be removed? Also, it would be good if the generated assembly is simple enough so the problem can be shown based on that, rather than having to run the code, but that might be tricky and/or cause the problem to disappear. I had hoped that this extra info might turn up an existing bug report about this, but no such luck it seems. What's weird is that it doesn't seem to happen for the non-lto case, doesn't happen when there is only a single analogWrite() call, and (NEW DATA!) doesn't happen if the -relax option is removed from the link command.Īh, that is awesome new info, since that gives a very strong indication of what is happening here (jump tables getting messed up by jump relaxation). Right now, PWM output only works on the pins with ![]() I probably won't have more time for this soon, though. I guess this either needs some debug prints (to read back various register values) or a JTAG debugger to verify what parts are correct and where the problem starts (or looking at the asm more closely and really verifying that all the values are correct). # I suspect this is the RAMPZ register, which contains the upper bits for a # This function continues with more case handlers connect pwm to pin on timer 0, channel A # The jump table ends here, and this is the first case handler # This jumps to 0x01af (word address, so byte address 0x35e) which seems sane # This is the jump table, the first entry for digitalPinToTimer(pin) = 1 # the table actually starts at 0x338 + 2). # starts at 0x338 and each entry is 2 bytes (note that a timer 0 is invalid, so ![]() # at 0x338 + 2*digitalPinToTimer(pin), which makes sense since the jump table tablejump2 below then doubles this value, so it ends up looking ![]() ![]() # around to add 0x19c, which is half of 0x338 which is where the jump table # (r30), extends it to r30:r31:r24 (little-endian, and adds 0x19c (by It takes the value returned by digitalPinToTimer(pin) # This checks for NOT_A_TIMER or similar, and jumps to 0x48c which handles that case # This loads the timer value from a progmem table (item inside the table is at 0x01A7) # Note that the pin number is constant propagated, only the val is passed in r24 ![]()
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