Hardware Reference
In-Depth Information
Can you match all the parts to the parts that you can see on your Arduino
Uno? Start with the main MCU (Part ZU4 in the schematic), the ATMega328p,
and all the breakout pins. Here, you can easily identify which ATMega ports/
pins map to the pins that are available to you in the integrated development
environment (IDE). Earlier in this appendix, you observed that PD0 and PD1
were connected to the USART TX and RX pins. In the Arduino schematic, you
can indeed confirm that these pins connect to the corresponding pins on the
16U2 (8U2 on revisions 1 and 2) USB-to-Serial converter chip. You also know that
there is an LED connected (through a resistor) to pin 13 of the Arduino. In the
schematic, you can see that pin 13 is connected to pin PB5 on the ATMega. But
where is the LED? By using net names, you can indicate an electrical connec-
tion between two points on a schematic without actually drawing all the lines.
Having every wire shown in a schematic might get confusing very quickly. In
the case of PB5, you can see that the wire coming out of the MCU is labeled
SCK
,
and that there is a similarly labeled wire at the top of the schematic feeding
through a buffer into a resistor and the familiar debug LED.
Most schematics that you'll find are done in a style similar to this one, with
lots of labeled nets that connect without direct wires. Continue to analyze the
Arduino schematic until you understand where all the signals are going. See
how many components you can match to the actual board.