I'm going to use Uno R3 together with a Proto Shield and with a Waveshare 3.5" TFT touch screen Arduino shield, which can make use of the ICSP instead of three I/Os (D11...D13) that can be conveniently left free for further development.
Hello, I ask you if there is a particular reason why the ICSP 2x3 header in the Proto Shield kit is provided with short connections, as if it is forbidden to stack these signals for use them on other shields.
Thank you in advance,
Alberto.
I am afraid not. The MOSI, MISO and SCK pins on the ICSP header are connected to pins 11, 12 and 13 on the board headers
Thank you, but I'm not convinced: if I check the schematic diagram of Uno R3, I see that the ICSP header refers to MOSI2, MISO2 and SCK2 signals controlled by U3 (Atmega 16U2) while MOSI, MISO and SCK at the digital I/O header are controlled by ZU4 (Atmega 328P).
This is the reason why I posted my question: in my mind it should be strange that two processors handle always the same way these two ports... why disturbing U3 if it could be possible to tie D11...D13 directly to the ICSP header?
Thank you for a deeper clarification.
Alberto
Arduino_Uno_Rev3-schematic.pdf (81.4 KB)
From the schematic that you posted
Pins 11, 12 and 13 are clearly mirrored on the ICSP header and I can confirm that having checked a genuine Uno R3 board