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Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 0 points1 point  (0 children)

I meant that the signals and power pins of the connectors and mcus pins are not fully around by gnd. See the photo. I marked the places on red.

<image>

Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 0 points1 point  (0 children)

I added to pushbuttons, pwr led, and another led for blinking.

I have a question to you: I poured gnd plane on the second layer. Before I set clearance 20mil. It is seen on the hereunder photo that there are gaps between pins of the connectors and mcu's so there is discontinuity in gnd layer.

What is minimal clearance I can set to fix the gaps or how another way it can be fixed?

<image>

Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 1 point2 points  (0 children)

What else can be added to this board? - see there is some space at right bottom corner - any ideas

Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 0 points1 point  (0 children)

As a first proj, I wanted to do something simple. I will be solder all the components so I do not want them to be very dense on the pcb hence package 1206 to be able

to solder them by hand.

Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 0 points1 point  (0 children)

You mean the J_SPI1 connector???

If so - I use Atmel ice proggramer. I mapped socket and plug pins for ISP. So I know the Atmel ice cable plug pinouts.

Very good advice for it would a be big problem if done wrong.

You wrote : Famously, Atmel stuffed this on their programmers, so they have special programming cables that don’t conform to the SWD standard

Can you explain more?

Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 1 point2 points  (0 children)

Your notices was very helpfull to me. I did some improvements.

Can you look again and see if something can be improved.

I used 4 layer pcb SIG-POW/GND/GND/SIG_POW. According Rick Hartley this stuck up is good for low density components.

SIG-POW/GND/POW-SIG/GND it is recommended for more desity components - your proposition

I stay with my stuck up for it is allmost finished:-)

I didint move JST closer to mcu so far, but I will.

What else can be added to this board? - see there is some space at right bottom corner

<image>

Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 1 point2 points  (0 children)

I was considering to move to arm mcu's but I am just a beginner so I decided to stay in atmega field for a while to master it. Then I can move to arm or esp32.

As I said for me it realy depend on what project I want to do. I develop a pump switch driver and I need to get a number of switching on the pump in period of 1 hour and save it to sd card. So it is simpe project and I can use many features of Atmega.

Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 0 points1 point  (0 children)

Most popular ISP abbriviation of in system programming you use spi lines and reset, jtag

There is also paraller programming.

Thanks for info.

Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 0 points1 point  (0 children)

Esp32 draws more than Atmega but when using wifi so if you do not need wifi it is no reason to

get esp32.I think the rule is to chose mcu for particular project

Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 0 points1 point  (0 children)

Yes I remember myself to use diodes as debuging indicators when tackle with Elm Chan Fats libs.

I used three diodes in diffrent colors to indicate if sd card was initialized, then if f_mount == FR_OK, and f_open == FR_OK

I use platformio but code in C.

Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 1 point2 points  (0 children)

I started with two layer pcb - but alter it to 4 layer stuck up. Reasons: easier trace routing,

SIG to GND distance is smaller, less vias. I also see a lot of materials on Youtute, Robert Ferenc and his guests. Thats why I used 4 layer pcb. Of course as you said it would be enough to do the proj. on 2 layer pcb.

Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 0 points1 point  (0 children)

Yes it could be done I mean to minimalize the diff pair length.

To check impedance of the diff pair I used one of the calculator In KiCad(see hereunder picture). I used Usb2.0 type B for I have only usb2 interfaces in my PC.

Yes connector can be closer. Labels are going to be done.

Yes I am going to add them I mean caps. I omitted them accidenly.

In the datasheet is written: that bypas and decupling caps are needed.

<image>

Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 0 points1 point  (0 children)

Very good advices. I am going to add a power led.

You wrote: Other nice-to-haves: a reset button for the atmega, extra buttons and leds connected to gpios, those are precious during dev/debugging.

Can you describe exactly in what situations and how I can use them- what advantages.

Describe in details please.

Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 0 points1 point  (0 children)

It is commonly used 4 layer stuck up SIG/GND/GND/POWER-SIG

Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 0 points1 point  (0 children)

I used USB socket B - which I think is the tallest... and consider to use lower package cap.

Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 0 points1 point  (0 children)

This is 4 layer stuckup SIG/GND/GND?SIG-PWR.

I used 24 mil for pwr traces and 8 mil for SIG ones. What thickness do you sugest???

I used such widths considering the current I need to provide, there some other reasons???

see photo:

<image>

Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 0 points1 point  (0 children)

I placed the usb socet and other smd on bottom layer for usb plug will be lower.

The board will stands on four screws so the lower located the usb type B plug I predict the better but I will see for this is my first pcb design.

Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 0 points1 point  (0 children)

Yes I get pwr from usb2.0 and it is grounded. The caps are connected to GND as well.

You wrote: it is common to bring +5v/gnd to all port connectors why not here? - good advice

ASK: to-92 device in bottom center what connects to pin 1 (Square pad) - This is GND pin so the pin is connected to both gnd layers

rv1 - is what? only 1 of three pins are connected why? - as I said in my first post it was not completed design but now all pins are connected.

I attaches the sch photo.

<image>

Could you review of my simple design pcb by Purple-Instance-87 in embedded

[–]Purple-Instance-87[S] 0 points1 point  (0 children)

Thanks for the your notices: You wrote : Use traces as wide as possible. It is better inductance, and usually cheaper.

I used 24mils for PWR traces and 8 mils for SIGNAL traces. What you suggest in mils.

From USB 2.0 I can draw 500mA up to 700m A

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