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18F2455 and sporatic results in COM window - Printable Version

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18F2455 and sporatic results in COM window - dmaners - 19-03-2016

Pinguino IDE 11.0 Beta 3
Windows 7 (64bit)
Pinguino 2455 v4 bootloader - 8bit

I have built several of these Pinguino's.
I have noticed that I get sporatic results in the COM window.
What I found was the power from the USB port was noisy.
The way I fixed it was, I placed a 104 multi layer cap across the power.
Now my results are flawless. Has anyone else run into this problem??

dmaners


RE: 18F2455 and sporatic results in COM window - mikronauts - 19-03-2016

It is standard practice to filter power supplies.

I generally use a 33uF or larger electrolytic or tantalum capacitor and a 100nF capacitor to filter Vcc.

On my Pinguino compatible PIC board, I have a 33uF and 100nF filter capacitor at each Vdd/Vss pair on the PIC18F4550.

http://www.mikronauts.com/robot-controllers/robopic-18f4550/


RE: 18F2455 and sporatic results in COM window - dmaners - 20-03-2016

(19-03-2016, 08:46 PM)mikronauts Wrote: It is standard practice to filter power supplies.

I generally use a 33uF or larger electrolytic or tantalum capacitor and a 100nF capacitor to filter Vcc.

On my Pinguino compatible PIC board, I have a 33uF and 100nF filter capacitor at each Vdd/Vss pair on the PIC18F4550.

http://www.mikronauts.com/robot-controllers/robopic-18f4550/

Do you find this necessary on USB power from a PC also?
I can understand if it was a transformed/regulated circuit.
When I look at it on the scope, it looks normal. Pretty flat.

Thanks

dmaners


RE: 18F2455 and sporatic results in COM window - dmaners - 20-03-2016

(20-03-2016, 12:26 AM)dmaners Wrote:
(19-03-2016, 08:46 PM)mikronauts Wrote: It is standard practice to filter power supplies.

I generally use a 33uF or larger electrolytic or tantalum capacitor and a 100nF capacitor to filter Vcc.

On my Pinguino compatible PIC board, I have a 33uF and 100nF filter capacitor at each Vdd/Vss pair on the PIC18F4550.

http://www.mikronauts.com/robot-controllers/robopic-18f4550/

Do you find this necessary on USB power from a PC also?
I can understand if it was a transformed/regulated circuit.
When I look at it on the scope, it looks normal. Pretty flat.

Thanks

dmaners

Well, according to the Pinguino schematics, I don't see any 33uf caps or any tantalums either.

Stupid me. But thanks for the attitude just the same.


RE: 18F2455 and sporatic results in COM window - mikronauts - 24-03-2016

- it does not hurt to add some filtering to the USB power, I'd probably add 100nF if I was already not filtering the mcu power with 100nF and 33uF

- It does not show up on the Pinguino schematic because the Pinguino board was not designed by me

- my design is Pinguino compatible, but it is not a Pinguino

- On my designs, I always filter the power to the microcontroller in order to try to reduce noise on the power line

- well-filtered power leads to more accurate (less noisy) analog to digital conversion, especially if there is a power utilization spike from a sensor

- what attitude? You must mean yours: "Stupid me. But thanks for the attitude just the same"


RE: 18F2455 and sporatic results in COM window - dmaners - 25-03-2016

(24-03-2016, 07:30 PM)mikronauts Wrote: Okay, Now I better understand. I referred to the Pinguino 18F2455. I thought that is what we were talking about.
When you referred to your board, it threw me off. And the attitude thing is because I asked a question, and you gave me the same answer. Once again, I thought we were talking about my project, the 18F2455 Pinguino board. 
Sorry, maybe some of my frustration came through my fingers. I appreciate the information. I will try to be more direct and patient.  Dave - dmaners


- it does not hurt to add some filtering to the USB power, I'd probably add 100nF if I was already not filtering the mcu power with 100nF and 33uF

- It does not show up on the Pinguino schematic because the Pinguino board was not designed by me

- my design is Pinguino compatible, but it is not a Pinguino

- On my designs, I always filter the power to the microcontroller in order to try to reduce noise on the power line

- well-filtered power leads to more accurate (less noisy) analog to digital conversion, especially if there is a power utilization spike from a sensor

- what attitude? You must mean yours: "Stupid me. But thanks for the attitude just the same"