Timeline for programming atmega2560 by ISP on self-made PCB
Current License: CC BY-SA 3.0
16 events
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| Apr 13, 2017 at 12:32 | history | edited | CommunityBot |
replaced http://electronics.stackexchange.com/ with https://electronics.stackexchange.com/
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| May 5, 2016 at 11:53 | comment | added | SamGibson♦ | @arckin : Please ask these new questions as a new topic, so that other members have the opportunity to reply. In my experience, there are big differences between different multimeters. Also see this previous question: electronics.stackexchange.com/questions/56066/… | |
| May 5, 2016 at 0:46 | comment | added | tuxben | forgot to ask you sthg : what are the can do and can't do regarding testing the continuity with an ohm-meter when it comes to mcu (due that the ohm-meter sends current)? Can I for example test the continuity between the MISO pin of the MCU and the MISO header pin? And when testing for shortcut, can I put the ohm-meter on a VCC pin and on the GND pin of the mcu? I am scared of damaging the mcu, of course. | |
| May 5, 2016 at 0:38 | history | edited | SamGibson♦ | CC BY-SA 3.0 |
Added update about requirement to connect AVcc.
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| May 5, 2016 at 0:26 | comment | added | tuxben | true, I haven't mentioned the AVCC, but it is actually connected to VCC. Thank you! | |
| May 5, 2016 at 0:19 | comment | added | SamGibson♦ |
@arckin : Thanks for the update. Note that, in my experience, AVR chips do not like having AVcc unconnected, even if you are not using the ADC (the datasheet specifies how closely AVcc must be to the Vcc voltage - an unconnected AVcc violates that requirement). You haven't mentioned connecting AVcc (pin 100 on the 100-pin package). If that pin is still unconnected, then you should expect incorrect behaviour! The same is true for the decoupling capacitors - reliable operation requires them (and in the right places). Good luck!
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| May 5, 2016 at 0:13 | vote | accept | tuxben | ||
| May 5, 2016 at 0:13 | comment | added | tuxben | Okay, while waiting for your answer I tried to solder a wire on pin 31. No capacitors for now. But it doesn't work. If I have time, I'll try your solution, but as you all say, I will need a lot of luck to make it work! Thank you for all your answers. I can't upvote your answer as I don't have enough reputation. I will accept your answer :) Again, thank you! | |
| May 5, 2016 at 0:01 | comment | added | SamGibson♦ | @arckin : "Do you think it might work if I hardwire pin 31 to the VCC rail?" - It might work, but personally I doubt it (at least, not work reliably). That still leaves several pins unconnected. As a start, I would add SMD decoupling caps physically between each pair of Vcc + Gnd pins (including AVcc and its adjacent Gnd), then use minimal lengths of wirewrap wire across the top of the MCU to link all the Vcc and AVcc pins (same with the Gnd pins). The capacitors give a larger physical "target" to solder, than the bare MCU pins - but the choices depend on PCB layout and other factors. | |
| May 4, 2016 at 23:46 | comment | added | tuxben | Yes, I will read all the rules of the document you gave me! Again, thank you for this precious information! Sorry, my question wasn't clear. Here is a pinout of the atmega2560 : here Only the pin 80(VCC) and 32(GND) are connected. Do you think it might work if I hardwire pin 31 to the VCC rail? "Also a partial workaround might succeed in allowing your MCU to be programmed - but it might not run reliably" - Yes, I'm aware of that :( | |
| May 4, 2016 at 23:32 | comment | added | SamGibson♦ | @arckin : "For my future design, I will follow this rule" - Note that the document I linked contains several rules. :-) "do you think that if I bring VCC to the same side, I might have a chance for it to work?" - Sorry, I don't understand. Please add a clear PCB diagram (or photo of an empty PCB) to your original question using the "edit" link, showing all of the MCU pins. Then readers might understand your additional question. And remember that any answer would be a guess. Also a partial workaround might succeed in allowing your MCU to be programmed - but it might not run reliably. :-( | |
| May 4, 2016 at 23:21 | vote | accept | tuxben | ||
| May 4, 2016 at 23:21 | |||||
| May 4, 2016 at 23:16 | comment | added | tuxben | thank you for your very detailed answer @SamGibson ! For my future design, I will follow this rule! thank you! Plus the fact that not all VCC, and not all GND are connected, the only VCC and GND connected are not even on the same side. As I have already done my PCB and that I need it to work for in a few day, do you think that if I bring VCC to the same side, I might have a chance for it to work? | |
| May 4, 2016 at 22:09 | history | edited | SamGibson♦ | CC BY-SA 3.0 |
Added link to a related question asked before, for PIC MCUs
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| May 4, 2016 at 21:59 | history | edited | SamGibson♦ | CC BY-SA 3.0 |
Minor grammer improvement
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| May 4, 2016 at 21:46 | history | answered | SamGibson♦ | CC BY-SA 3.0 |
