Standalone pro mini pcb

Other Hardware 3rd Party Boards
1

Hi,

I am looking to use the standalone pro mini circuit as part of a larger circuit that will be made into a pcb for a project i am currently working on.

I have a few questions based on the pro mini 328p schematic http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Dev/Arduino/Boards/Arduino-Pro-Mini-v13.pdf
datasheet
http://www.atmel.com/Images/doc8161.pdf

This will be powered by a 3.7v Lipo battery (3.5 - 4.2V). The RAW pin on the schematic can be ignored since the VCC will just be the Lipo battery, and not regulated.

  1. If i just use the internal clock (8MHz), do i just leave pins 7 and 8 open?
  2. If there is no LED attached to pin 17, SCK, do i leave pin 7 open?
  3. I will use the I2C lines. Should i use the pullup resistors? and what resistance should they be?
  4. In terms of programming with Arduino, can i just use the FTDI Basic board (3.3V or 5V) to upload the program or what should i do here?

Thanks a lot for your time,
Jeff

2
  1. yes
  2. yes. Any unused IO pins should be set to Input and have their internal pullup resistor enabled so they don't oscillate & consume power.
  3. yes.4.7K to VCC. Maybe lower, depends on your I2C loading. More parts = lower resistor value. 3.3K, 2.7K. 4.7K should be good starting point.
  4. search for a recent forum posting (Thurs, Fri) for installing bootloader into internally clocked device. Requires fuse change to use internal oscillator vs the external crystal board types. Then you can use FTDI Basic or equivalent.
3

Thanks a lot for your response.

Is this the post you were referring to Minimal circuit standalone operation - Microcontrollers - Arduino Forum?

In the post, this is referred to,

So after using this method, i can then use the FTDI basic for uploading programs?

Cheers

4

Should be able to.

5

Should be able to.

Would it matter what FTDI Basic board is used?

3.3V

5V

Cheers

6

No. 8 MHz promini (equivalent) will work fine powered from 5 V also.

7

Jeffro_Aus:

Should be able to.

Would it matter what FTDI Basic board is used?

3.3V
https://www.sparkfun.com/products/9873

It might...

The Mega328 will be fine but that board uses the FTDI chip's internal regulator to get 3.3V. The 3.3V output from FTDI chips is only 50mA.

8

The FTDI power connection connects to VCC on the promini - so if the FTDI is set for 3.3V, the 328 will see 3.3V for its Vcc. And if set to 5V, the 328 will see 5V. 50ma is plenty for programming.
An 8 MHz board will program correctly with either voltage.