Need someone to fabricate this for me

Hi,

I cannot volunteer to do this, but I can suggest an alternative; if you don't have the tools or experience for this, you're better off ditching the castellated board which makes no sense if it is carrying just the microcontroller, crystal and a couple of passive components, and just redesigning the board on the left to carry the TQFP version of the chip, which has fairly large 0.8mm pin spacing, and is hand-solderable with a normal iron, no need for hot air tool skills. The TQFP part will take up less space than the castellated board, so it will fit. It would be a cleaner, lower-profile and more reliable solution.

Castellated boards kind-of make sense for (say) ESP boards because they contain more circuitry as a module, and also radio circuitry to simplify the end product. Here it's not simplifying, it's making it more complicated.

Also, the left side board is large, you could also go for a larger crystal and passives, if you feel you have the space for that. I can't tell if you're using 0603 or 0402.. 0402 is more unreliable for manufacture, I don't think it's worth the effort (unless there's a technical reason for using 0402).

Hi, The reason for the Castellated holes version is so that i can use the same module for other projects in the future, Instead of having a full arduino with pin headers taking up valuable room, i could instead go for a module that keeps a low profile while providing everythhing i need, Also i regrettably went with 0402 and it was a terrible mistake, I only have space where it is on the PCB due to how the xbox from panel connects to the front. I guess i could go with the TQFP version as well but preferrably would want to keep with this module idea for future projects.

Thank you for your feedback though and i guess i could make a prototype using the TQFP version. Also do you suggest any other crystals to use because they are really small and again, hot air rework/soldering those sized modules is really difficult

Here are closeup images of the PCB layout, i believe i have all the bare minimum components needed for this to function, the 100nF cap on the AREF so i can use analog inputs and the 10k resistor on the reset and VCC to stop random resets and allow the resetting of the ATMega.

The 16Mhz crystal not sure if actually needed to get it working as i can use 8Mhz i believe.

Thanks

From an EMC point of view it's not ideal - the ground plane is nearly cut in two.

I don't see any load capacitors for the crystal (if it's actually a ceramic resonator it may not need them).

The system should start up on it's internal clock so the crystal shouldn't matter if you don't use it.

How are you trying to programme it - does this programming process work with other parts ?

MK

They are ceramic Resonators yeah, And as for programming i'm using Arduino as ISP as you should be able to do that with these. i have done it successfully before using a DIP package ATTiny and a QFN version of the ATTiny but this doesnt want to play nicely.

Can you post a picture of your programming set up and explain exactly what happens when you try.

MK

I dont currently have everything setup but basically involves an Arduino Uno with 6 Dupont cables coming from the uno to the test points on the module, Using avrdudess to attempt to read the fuses results in signature 000000. I also made test boards with every pin exposed on the ATMega but also gives the same result. Maybe the resonator stops it from working?

But at this point i am out of ideas

If you are in the UK you could send me a little board and I'll see if I can get it going.

I'd need to solder little wires to the castellations and I'd hang a scope on the SPI bus to see what it's doing.

I've got an Arduino and I've got various Atmel AVR aids (although it's quite a while since I did anything AVR based).

MK

I can send you them no problem, Would you like a completed board and a chip and blank PCB with resonator too?

That way if you can get it working, you probably have a better chance of soldering it and getting them working.

I can send you the 0403 resistors and caps too if you would like?

May as well send everything, my postal address is in my E14 profile -  I think any one can access it but if not please let me know.

MK

Can't find your address on your profile. Let me know what it is and i'll get them shipped to you quickly

Thanks

MK Electronics Ltd,

Unit 4,

Greenlaw,

Castle Douglas,

DG72LH

I'll look forward to it.

MK

MK Electronics Ltd,

Unit 4,

Greenlaw,

Castle Douglas,

DG72LH

I'll look forward to it.

MK