OLIMEX© 2017
OLIMEXINO-32U4 user's manual
7.3 UEXT
OLIMEXINO-32U4 board has UEXT connector and can interface Olimex's UEXT modules.
For more information on our UEXT modules please visit:
https://www.olimex.com/Products/Modules/UEXT/
Pin # Signal name
1
VDD out (3.3V or 5V)
2
GND
3
D1(TXD)
4
D0(RXD)
5
D3(SCL)
6
D2(SDA)
7
D14(MISO)
8
D16(MOSI)
9
D15(SCK)
10
D13(UEXT_#CS)
IMPORTANT: Be careful with the voltage output available at pin #1. The on-board 3.3V/5V switch
also controls the voltage output available at pin #1 of the UEXT. Do not connect Olimex modules
when the switch is set to 5V position, unless you are 100% sure that these UEXT modules work fine
at 5V (most Olimex modules can not work properly at 5V, only at 3.3V)
It is important to note that there are 4.7k pull-up resistors on the I2C lines – SCL/SDA (D3 and D2
respectively). You can disconnect/disable the resistors by cutting between the pads of the small
SMT jumpers R11_E and R12_E.
The chip select pin – CS (D13) also has a 4.7k pull-up resistor which might be disabled by cutting
R13_E.
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