Propeller fried ???

propelleruser999

Propeller fried ???

I have made a veroboard with a 40-Pin Dip Propeller, very similar to the protoboard.
This board worked at the spot with downloading to RAM. With downloading to EEPROM i had a success rate of 100%, but with executing from EEPROM succes rate was only 80 to 90%.
Reason probably is, that i use ATMEL 24C256 devices, , which are specified for 5 Volt operation.
So i today connected them to 5V and added a 1.47K resistor to pin 29 (SDA), but none in between Pin (28) and SCL.
After applying power, my 3.3V power rail ran up to 4.2 Volts and no more access to the EEPROM was possible.
I tried this several times and sometimes the 3.3Volts stabilizied to 3.3Volts and i got my EEProm-progams running.
But now all communcation to EEPROM is dead, cannot write to or read from EEPROM anymore.
Is PIN 28 a read/write Pin, then i know what i did ( need a new prop ?)

hippy

It could be fried; the supply went well above maximum for the Propeller. Have you removed the Eeprom and tried downloading to RAM ?

propelleruser999

Yes, downloading to RAM still works and all programs (LEDs, FemtoBasic,VGA,etc.) are executing correctly. When downloading to EEPROM it gives me an error during verifying EEPROM content.
So i think i fried pin 28 (SCL line).

stevenmess2004

That almost sounds like a problem with the eeprom rather than the prop. If downloading programs to RAM still works than hook a led upto pin 28 (after disconnecting the eeprom) and write a small program to flash the led. Also check if you are getting input from that pin. If that doesn't work than the pin is cooked. Otherwise it could be the eeprom.

Peter Jakacki

You don't need a series current limit resistor as the EEPROM is never sourcing only sinking, that's why you always need a pullup resistor on SDA. It's the pullup resistor that needs to go to +5V. The pullup can be around 10K. If your arrangement had the series resistor from the eeprom to the prop with a pullup then you will not get it to work as that forms a voltage divider so that the 24c256 could never send a logic low that would be recognized as such. If it was the other way round the prop could not send a logic low. You didn't mention the pullup or it's value.

*Peter*

P.S. As the SCL line works fine it is very possible that the pullup only needs to go to 3.3V as well.

Post Edited (Peter Jakacki) : 4/12/2008 7:42:52 AM GMT

propelleruser999

i have 10K pullups to 3,3V on both SDA and SCL line. When running the 24C256 with 3,3V every thing worked fine, except appr. 1 out of 5 times it wouldn´t start from EEPROM.
so i hooked 2 LEDs to pins 28 and 29 and started a small program to let them flash. They did. However scoping the pins showed,that pin 28 has a voltage swing of 0 to 3,3V, while pin 29 only shows 0,5 to 3,3V. this is a 8 LED bar,so i scoped the other pins to. all have a voltage swing from 0 to 3,3V, only pin 29 has 0,5 to 3,3V.
i have run FemtoBasic to check the pins for input, but i dont know the syntax for INA

10 A=INA 28
20 B=INA 29
30 PRINT A,B
40 GOTO 10

didn´t work.

stevenmess2004

Just try a short spin code something like this

CON
 clockmode...
 freq...
OBJ
  tv : "tv_text"

PUB main
 tv.start(12)
 tv.bin(INA[noparse][[/noparse]28..29],2)
 waitcnt(cnt+clkfreq*2)
 tv.out(13)
 tv.bin(INA[noparse][[/noparse]28..29],2)
 waitcnt(cnt+clkfreq*2)
 dira[noparse][[/noparse]28..29]:=%11
 outa[noparse][[/noparse]28..29:=%11
 tv.out(13)
 tv.bin(INA[noparse][[/noparse]28..29],2)

Peter Jakacki

Are you saying that it only pulls down to 0.5V? There should not be a problem with accepting 0.5V as a logic low but then again it shouldn't be that high. So if you disconnect everything from pin 29 does it still read 0.5V?

You know that with the power off you can check to see if a chip has fried it's pin by using your trusty old meter on diode check. Red probe on ground and with the other probe you are measuring the internal substrate diode which should all be in the same ballpark. Same goes if you put the black probe on the supply pin and check that way as well.

*Peter*

propelleruser999

i tried your spin code. had to modify it for VGA and add a bracket.
pins 28 and 29 work as inputs and outputs. i have now replaced all 3 EEPROMs and reprogrammed new ones. the EEPROMs are selectable via a rotary switch. all 3 were fried;i dont know why.
but those are only 2$ parts and the propeller has survived .
I have now booted from different EEPROMs appr. 30 times without a failure.

thanks to all for your help.

stevenmess2004

Looks like that eeprom comes in three variants. One each for 4.5V to 5.5V, 2.7V to 5.5V and 1.8V to 3.6V. You haven't got the 1.8 to 3.6V ones do you?

propelleruser999

No, i have the 4.5 to 5.5 variant. My main distributor doesnt carry the other ones. I've later ordered 1.8V to 3.6V versions at another distributor, but they send me SOIC versions (unsolderable for me, at least not on a Veroboard).
But the 5V variants worked with 3.3V during programming always and during booting 80-90%. Now that i feed them with 5 Volts it looks much better (with 1.47K series resistor and 10K pullups).

PS.: just experienced first fail to boot after appr. 100 boots. that's ways better , than before; but not reliable enough. I also encountered,that misboots occur more often, when battery operated,than when fed from a power supply ???

stevenmess2004

If your running it off a battery than a low battery could be the culprit. Is the program the same for all boots?

propelleruser999

Stevenmess2004,
i plan to give a demo of the power of the propeller to some companies next week. currently they use high perfomance pc equipment and expensive hardware, like X/Y/Z controllers, etc.
One of my plans is to show, that the prop can run off a single 9 Volt NIMH battery for at least 6 hours.
Yesterday charged (9,54 Volts), today it has still 9 Volts( 8,65 Volts under load) after 300 reboots for my EEPROM testing.
For the demo i will store different programs in the EEPROMs.
For my private use i store functional programs into one EEPROM, testing/debugging is done either in RAM or on another EEPROM.
Currently i have 3 EEPROM sockets,which i can select via a rotary switch

propelleruser999

i have now appr. 300 reboots from EEPROM. 4 fails so far.It appears to me, that the fails are dependant on the off-time of my propeller board. if its more than 10 minutes off, the probability is much higher than if i cycle it within a minute. All EEPROM boot fails occured after i had a break. Can it be a problem with the powerline caps. On the 5V regulator i have ??? (cant read it,because cap has been glued down to the board backwards to the capacitance print), after the 3.3V regulator i have 100uf. Directly to the processor pins i have 0,33uf on both sides of the DIP power pins.Do i need more caps, e.g. on the EEPROMs ?
There is no more hardware on the board. All plug-in modules have no caps at all and function properly.

hippy

propelleruser999 said...
after the 3.3V regulator i have 100uf.

That might be causing slow rise/fall times on the 3V3 either interfering with Propeller reset or Eeprom operation. You could try removing it and see what that does.

propelleruser999 said...
All plug-in modules have no caps at all and function properly.

You could try adding caps, and does it boot more reliably without the plug-in modules ?

Trim it back to the bare basics ( flashing LED, TV Text or something ) then when you have reliable re-booting start adding things.

Post Edited (hippy) : 4/12/2008 6:23:27 PM GMT

propelleruser999

hippy,
i just looked up the protoboard schematic. they use 10uF as filter cap for the 3.3V. so i will change my 100uF to 10uF and try again. If i watch the 3.3V with my scope, it takes appr. 1/2 second for the 3.3V to come fully up.
this boot problem occurs also without any plug-in modules , just a simple led flashing.

I just changed the cap to 10uF, i think its even worse.I can now wait only 2 minutes and the prop doesnt boot anymore.Cycling the power switch once more and it always worked.
I also tried with no 3.3V filter cap at all. Thats worst case;boots every second time only.

stevenmess2004

What are you using to power the eeproms? Are they on the same power supply or a different regulator? Can you check if the power to the eeproms is taking longer to rise to the right voltage?

propelleruser999

Its simply a copy of the protoboard power: 5V regulator followed by 3.3V regulator. since i power the eeproms now from 5V it should be earlier up than the 3.3 Volts. I had the same problem, when i powered them from 3.3 Volts, but much less frequently. Since i have the 5 Volt version of the EEPROM,i changed eeprom power to 5 volts, but it even got worse.

stevenmess2004

I wasn't paying attention before

propelleruser999 said...
i have 10K pullups to 3,3V on both SDA and SCL line

These pullups may need to go to 5V depending on the logic levels the eeprom expects. Make sure that you have a series resistor to protect the prop though like this

eeprom---------+--------/\/\/\/\----prop
                       |
                      +------/\/\/\/\--5V

Peter Jakacki

Steve, there is absolutely no need for a series resistor as it is completely redundant. If the eeprom sourced +5V then you would need it, but it can only sink current due to it's I2C bus which relies totally upon pullups so that multiple devices can be wired "OR" fashion. The pullup resistor limits the +5V that it sources, simple as that.

From what I can tell there is nothing fried about the Prop however an old 24C256 datasheet lists the minimum high input voltage as 0.7VCC which is around 3.5V. RTM, basically the 24C is not compatible with prop logic levels and the OP is simply trying to fit a square peg in a round hole because that's what he's got. No need to bang out our brains for that. Not very helpful I know but he just has to get the right chip or fudge some kind of level shifter (ugghh).

*Peter*

stevenmess2004

Peter, if you choose the resistor values correctly than shouldn't you be able to arrange for greater than 3.5V when idle (DIRA=0) and less than that when the pin is pulled low? Shouldn't that solve the problem? Happy to be proven wrong though.

Peter Jakacki

Yep, and that's fudging it like I said. The reason I made the remark about the series resistor is because you mentioned it as protecting the prop, not so. It is true that you can do level shift with the same configuration but it's a balance between getting a good logic high and still having a good logic low while maintaining rise/fall times. Fudging.

*Peter*

P.S. Glad to see someone picked up one of those cheap TV displays, wish it was VGA though.

stevenmess2004

Fair enough. Who cares if its fudged though as long as it works reliable . Isn't that what engineers are for

Peter Jakacki

If fudging could get it to work reliably or if he had no other choice I would recommend that solution but there is so little margin to operate with that if I were the OP I would spend a couple of dollars and just get the right chip. That's what engineers do

*Peter*

hippy

propelleruser999 said...
Its simply a copy of the protoboard power: 5V regulator followed by 3.3V regulator. since i power the eeproms now from 5V it should be earlier up than the 3.3 Volts. I had the same problem, when i powered them from 3.3 Volts, but much less frequently. Since i have the 5 Volt version of the EEPROM,i changed eeprom power to 5 volts, but it even got worse.

Put a 3V3 Eeprom in and make sure the hardware is reliable before buggering about trying to use the 5V Eeprom. Otherwise you don't know what problem you are battling; is there something fundamentally screwed with your circuit implementation or is it just an issue with 5V Eeproms.

propelleruser999

okay hippy,
i got your message (however buggering has some bad meanings in german language, i think you didnt mean it that way (Scheisskerl,Sodomie, Analverkehr and other bad things)
Will ty to order Monday 3.3V dip devices. I have followed the thread "5 Volt devices to the prop" , but if the 24C256 is really only a sink device, what caused my 3.3 voltage going up to 4.2 volts ??

propelleruser999

sorry hippy,
but my last append has been filtered out (my german google translation didn´t get through the filter for the word "buggering", some bad words after translation)

Will try to order Monday 3.3V dip devices. I have followed the thread "5 Volt devices to the prop" , but if the 24C256 is really only a sink device, what caused my 3.3 voltage going up to 4.2 volts ??

Peter Jakacki

999, I read you...
The problem with interfacing from +5V levels that rely upon current limiting is that the input voltage is clamped by the substrate diode to +3.3V. That means that a small amount of current will flow to the prop's supply rail which is not a problem as long as there is sufficient load on the supply to absorb this current otherwise the voltage will
rise. This happens at reset when the prop is in standby or any other time when it is drawing mininmal power. The voltage rises until some internal structure breaks down and
clamps the voltage (around +4V). This may be non-destructive but what is temporarily breaking down and does it affect the operation of the prop? Who knows.

Quick solution: Add a 1K (or less) resistor between the +3.3V rail and ground, at least to test this out.
Another VDD clamp that I use is simply two red leds in series with a 47R resistor. The leds act as excellent low-voltage zeners as LV zeners are too sloppy for this.

As Hippy mentioned it is good to check your circuit with the real devices, but once you do that why would you use the 24C version again?

*Peter*

P.S. "buggered" is a common Aussie/English expression for something that's stuffed (i.e. broken). It is perhaps a word we should not use because of it's proper meaning.

hippy

If we stopped using words because they had multiple, regional and even colloquial meanings and have evolved from what they may have meant in the distant past we'd likely be stuffed run into no end of difficulties

"Buggering about", in UK terms, would probably best translate as fruitlessly expending energy in a direction that was not the one which would best achieve the desired results.

Now I'm going out to find a *** and come home with sticky buns - a cigarette and sugar coated cakes

Philldapill

Wow. Thanks for the clarification there hippy. LOL

QuattroRS4

LOL hippy ... bet if a few people watched 'snatch' they wouldn't even recognise that english was used !

rgds,
John T

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