So i am trying to make a PCB design for my atmega32 but i want to make it minimal , i have a development board but it has too many stuff , i just want to the avr , a crystal , a reset button and a power input.
Is there any place i can find what i am looking for ? the datasheet , a website? if someone has done it before would mind sharing ?
thanks a lot in advance!
The device is different, but I made something like this.
What "minimal" indicates will vary from person to person.
If I want "minimal", I don't need the reset button and will add a debug interface instead.
There are multiple options for "power input" alone. Is it a DC jack? Is it microUSB?
Welcome to the Forum.
Do you need guidance on HOW to make the power supply, (regulator, caps, etc), or just what is needed to make the micro work?
Look at the data sheet for the micro's pinout, in whatever package you intend to use.
As a general rule:
ALL Vcc pins need to be connected to V+.
ALL Ground pins need to be connected to Ground.
AVCC needs to be connected to V+, either directly, or through a small LC filter.
AGnd, Anaolog Ground, needs to be connected to Ground.
EVERY Vcc and AVcc pin need a 0.1 uF by-pass cap from the pin to Ground.
These caps should be as close to the micro's pins as possible.
ARef needs a 0.1 uF by-pass cap from the pin to Ground.
Do NOT connect ARef to the power rail.
(Unless you really, really, know what you are doing and specifically why you need to do this.)
The Xtal pins should have the external Xtal close to the micro, and each pin will need a cap to Ground.
One of the Application Notes shows putting a small ground plane under the Xtal and its caps.
That's nice, but in practice it isn't necessary for a general purpose testbed.
The Reset\ pin has an internal pull-up resistor to Vcc, (inside the chip).
Many people add an external 10K pull-up resistor from that pin to Vcc.
For a testbed you probably want to add a normally open push button switch from the Reset\ pin to Ground, so that when debugging code you can easily reset the micro.
Many designs would include a 0.1 uF cap from the Reset\ pin to Ground.
Most programmers will work fine with that in place.
Occasionally a programmer will have difficulties with that cap in place.
All of my boards include it.
How will you program the micro?
Point being, you will want to add a 6-Pin male programming header, so that you can connect a "standard" AVR ISP programmer to the micro to load your program.
Ask if you need help with the pinout.
It is in the data sheet, and is similar to the Arduino schematics.
If you are making a PCB you might well wish to add a small on/off slide switch.
It makes it much easier when cycling the power to the board.
Often, even on minimalistic boards, one might route one of the I/O pins to a resistor and LED to ground.
You don't have to install those parts if you don't wish to, but it makes it easy to test the brand new board once you solder it up.
You could even put a 2-Pin male header on the board for the I/O pin to the LED, or not, as desired.
Finally,
You probably ought to put your initials and a date on the PCB.
As you make many boards over the years it will help you keep track of which board is which.
Mounting holes in the corners are also useful.
Labeling which micro goes on the board, in text on the board, is also useful, (down the road).
Putting a large Pin #1 marker on the board, for the micro's Pin #1, and for the Programming Header's Pin #1, is also very useful.
Having a spare pad for a Ground Pin for an O'scope or Logic Analyzer or DMM is also very useful.
Good luck with your board.
JC
Edit: Typos
An Arduino nano is minimal, at least consider what is on its schematic as minimal, and substitute your M32, but it will be cheaper to just get the nano.
jim
i just meant they least minimum to get it running
yes i meant a DC jack
Is there any place i can find what i am looking for ?
Yes - The Product Page !
https://www.avrfreaks.net/commen...
https://www.avrfreaks.net/commen...
There is an Application Note on AVR hardware design ...
least minimum
Wouldn't that be the maximum ... ?
thank you so much for taking time to help me!!!
i really appreciate these instructions and will follow it.
yes i will make a pcb , not a development board.
I don't need a power off/on switch or programming the avr it will already be programmed.
I would consider "minimum" to include the following:
1. Connection of all power supply and common pins to a power supply jack/connector
2. Proper power supply bypass capacitors AT (or very close to) the micro pins, not out on the header
3. Proper connection of AVcc to the common Vcc net of step 1. If an isolating resistor or inductor (and corresponding capacitor) is recommended by the spec sheet, include those.
4. Programming connector suitable for the micro concerned.
5. Breakout pins for all of the MCU pins NOT involved in the preceding steps.
6. I would probably add pads for a crystal and associated caps. Pads cost little or nothing. Crystal operation is ofter miserable out on the breakout pins.
Jim
Programming connector
I'd say include debug in that.
Yes, certainly, programming + debug. Didn't know what an M32 offers.
Jim
Cute lil' PCB, kabasan, but I'd have given the caps their own layout instead of having to glue them to the pins later on. I do like the GND test point, though - I put them on all my boards, and get somewhat cranky when people don't! S.
I do like the GND test point, though - I put them on all my boards, and get somewhat cranky when people don't! S.
See my recent post in the Tutorials forum.
Cute lil' PCB, kabasan, but I'd have given the caps their own layout instead of having to glue them to the pins later on.
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