SPI on a perfboard.

[KansaiRobot]

Hello and thanks always.

I am building a system using SPI. I have implemented several configurations on a breadboard and they work great. I use the following boards (sorry in japanese) that are basically fancy versions of the PIC 18F4553 and 18F2553.

https://akizukidenshi.com/catalog/g/gK-06720/

https://akizukidenshi.com/catalog/g/gK-08010/

I also use a simple PIC 18F2550

The problem is when I tried to put this configuration on a perfboard, they fail. In one case they transmit correct characters sometimes and incorrect other times. In the other case the slave only transmits 0xFF.

I have checked and double checked. The connections are ok. The programs work (on the breadboard that is) correctly. I have run out of ideas of what could be wrong.


I know it is a mess of cables but I ve originally neat thin lead cables on the back but they didn't work so I ve tried these cables...

Any, and I mean any ideas that can give me some light are welcomed. Need some help here.

 

[ericgibbs]

hi KR,
Do you have a circuit diagram that you could post.?

This is a diagram of the 18F2550, SPI project that I use, works OK.

E

 

[KansaiRobot]

Thanks for the post
Here you are

This schematic works perfect on a breadboard btw.

 

[Mikebits]

Thanks for the post
Here you are
View attachment 93958
This schematic works perfect on a breadboard btw.

Wait, you said it does not work on a breadboard as in your picture with long wires, so which is it, it works or not? Do you mean it works if you run a simulation? I am having trouble viewing your schematic.

 

[atferrari]

This schematic works perfect on a breadboard btw.

Does it, really?

 

[tunedwolf]

I don't see much in the way of power supply decoupling there, maybe try adding a few 10uF and 100nF caps across the supply pins to your modules?

 

[KansaiRobot]

Wait, you said it does not work on a breadboard as in your picture with long wires, so which is it, it works or not? Do you mean it works if you run a simulation? I am having trouble viewing your schematic.

Thank you fro the reply

It works without problems on a breadboard.

It does not work on a perfboard (as in the picture)

No simulation performed.
ummmm I see the pic gets too small... how about this?

 

[KansaiRobot]

Does it, really?

Yes... why??

 

[KansaiRobot]

I don't see much in the way of power supply decoupling there, maybe try adding a few 10uF and 100nF caps across the supply pins to your modules?

Could you explain this to me please?... you dont mean caps between 5V and ground, do you?

 

[tunedwolf]

Could you explain this to me please?... you dont mean caps between 5V and ground, do you?

That's exactly what I mean. Now that I have looked again at a close up of the photo you posted, I can see that you have fitted 100nF caps across the supply pins, try adding say a 10uF cap right beside each of them. Also, keep your inter-connect wiring short.

 

[atferrari]

s

Yes... why??

In your OP you say that it does not work.

 

[granddad]

On any of your pic's I would not let the PGM pin float , check the data sheet .... did you have to cut any tracks on this board or is it just pads ?