atMega8 eagle layout - Page 1
Forum section: electronics / general

author: B_S
author_rank: Newbie
timestamp: March 15, 2014, 09:24:01 pm
content: Hey guys.I'm little puzzled here and hope for some advices. My current project is to buid the USBasp atmel ISP programmer.I used thishttp://www.fischl.de/usbasp/usbasp_gr.rarlayout to etch the pcb. The quality of the result was very promising but i got a pinout problem. Because initially baught the components for the original scematics i only have the atmega8 but the layout i etched requires the atmega8-p. afaik the diffence between the atmega8 and atmega8-p is only the power consumption and the DIP package should be the same? ( sorry but i didn't find a datasheet for the atmega8-p )Now my problem is that the pin gap on the pcb is smaller than on my chip ( i will upload some pictures tomorrow ).I printed the layout using eagle via normal print option of this tool, it's my second self etched pcb so my question is: is there anything i need to consider etching the pcb or do i just need the atmega8-p controller?thanks,B_S

author: madires
author_rank: Super Contributor
timestamp: March 15, 2014, 09:40:07 pm
content: The ATmega8-P is the pico power version of the ATmega8 with exactly the same pinout. The center of the pads for the DIL package should be 2.54mm apart. If the spacing for other components is also too small you might have a scaling problem with your printout.

author: uwezi
author_rank: Unknown
timestamp: March 15, 2014, 09:42:40 pm
content: Quote from: B_S on March 15, 2014, 09:24:01 pmI assume you are talking about an SMD package for the ATmega...The ATmega8, 48-328, 48p-328p come in DIP28 and in different SMD packages:32 TQFPpitch 0.80 mm32 MLFpitch 0.50 mmSee the section "Package information" in the datasheet you found...If you are getting a different pitch for a DIP package, then you have a problem in the printing process. Especially you need to make sure that your printer driver does not change the scale of your printout!

author: B_S
author_rank: Newbie
timestamp: March 15, 2014, 10:20:52 pm
content: Nope, there are no smd components. Eagle tells me for the atmega8-p: DIL28-3. It's very strange because i'd have to bend the pins a little bit to fit but it should fit without bending the pins ( yep i know you have to bend the pins "inside" to fit but not towards each other ).

author: uwezi
author_rank: Unknown
timestamp: March 16, 2014, 11:18:52 am
content: Is this the longest component you ever had on a circuit board?The problem with a non 1:1 reproduction for the circuit boards gets worse the longer the device is.I assume that when printing the layout, you had "fit to page" enabled in the print dialog.

author: B_S
author_rank: Newbie
timestamp: March 16, 2014, 12:32:00 pm
content: @uwezi: Yep, it's the longest component and i didn't print the layout myself, cause i don't have a laser printer so I sent a PDF ( scaling factor 1 in eagle ) to a friend to print it. For the next try I'll keep in mind to disable the fit to page option in the printer dialog.Thanks a lot for the response.

author: uwezi
author_rank: Unknown
timestamp: March 16, 2014, 01:46:04 pm
content: Also make sure that your friend prints the PDF file in 1:1 scale and not as "fit to page".The possible complication is, that both the PDF-reader and the printer driver offer independent scaling options...