Datasheet

7 | Page

 At the left there are the GND (white) and 5V (Purple) connections.

 At the top row right are the Reset (green), Mosi (Red), Clk (Black) and Miso (Grey)

 The equivalent JTAG names for these are: nSRST, TDI, TCK, TDO

3.3 Using/running the Atmega-328

When the device has been programmed it will run that program independent of the Raspberry-

Pi. In fact you can remove the board from the Raspberry-Pi and use it standalone.

When developing programs you may leave the jumpers in place as the programme will tri-state

its pins and set the reset pin high when it has finished. This is NOT the case if the PI is reset or

not powered. Especially the reset-jumper needs to be removed otherwise the Raspberry-Pi GPIO

pin 8 (which is default low) will the keep the 328 device in reset or you can run the reset_off

script.

You should also remove the jumpers if you want to use any of the following pins: B3,B4,B5,C6.

4 Atmega-48

4.1 Features

This device is intended to be used as Real Time Clock (RTC) and/or as IRDA front end. However

it is also freely programmable by the user and thus can be used for any other application, giving

the user the power of not one but TWO Atmega devices to play with.

Note: The I2C interface of the Atmega-48 is connected permanently to the Raspberry-Pi I2C

interface <GOIO0/1 on rev1, GPIO 2/3 on rev2>.

Also beware that if you make programming errors with the Atmege-328 the device can easily be

replaced. This is not the case with the Atmega-48. It is therefore strongly recommended that

you are extra careful and do not damage any of the I/O ports.

Spare connections.

The following I/O pins of the Atmega-48 are not used and are brought out to a connector:

B0,B1,B2, B3, B4,B5, C0,C1,C2,C3,D0,D1,D4, D5, D6, D7.

Beware that B3, B4 and B5 are also used for programming the device.

4.2 Program the Atmega-48

To program the Atmega-48 from the Raspberry-Pi you have to place the following 4 jumpers:

The programming is the same as the 328 but replace "328p" with "48pa".

The colours used here are the same as on MY squid cable but I can't guarantee all squid cables are the same.