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Schematic question... (Read 2912 times)
03/27/09 at 12:45:37

Starfire   Offline
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More of a curiosity thing I was looking at the schematic for the new Arduino Mega compared to the Wiring board and I noticed the ISP port on the Arduino routes to the MISO and MOSI pins, while the Wiring routes to the RX and TX pins.  Are these exchangeable since the ATmega128 on the Wiring board has the MISO, MOSI pins but they are unused.

Just trying to get more of an understanding.  Smiley

Thanks!
 
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Reply #1 - 03/27/09 at 15:03:30

barragan   Offline
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hi Starfire, from the atmega128 datasheet on page 300 we can get this:

Even though the SPI Programming interface re-uses the SPI I/O module, there is one important
difference: The MOSI/MISO pins that are mapped to PB2 and PB3 in the SPI I/O module are not
used in the Programming interface. Instead, PE0 and PE1 are used for data in SPI Programming
mode as shown in Table 127.

MOSI (PDI) PE0 I Serial data in
MISO (PDO) PE1 O Serial data out
SCK PB1 I Serial clock


this I used in the design for the Wiring I/O board, that´s why the ISP pins are wired to the PE0 and PE1.

The datasheet is located here: http://www.atmel.com/dyn/resources/prod_documents/doc2467.pdf
 
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