
Shield pin configuration
2.6
Pin direction and pullup control
For most shield pins on the Intel® Edison kit for Arduino*, there is a buffer/level-shifter which needs to be
configured for input or output direction, and an external 47 kohm pullup/pulldown resistor, which may be
optionally enabled. Both are driven by dedicated GPIO outputs, listed in Table 7. When configuring a shield pin as
an output, we advise configuring the buffer for output
before
setting the SoC GPIO pin direction to output. To
disconnect the external pullup/pulldown resistors, it is necessary to configure as high-impedance inputs the GPIOs
that drive them.
Note also that the GPIO signals from the PCAL9555A GPIO expanders have internal 100 kohm pullup resistors,
which are connected to the GPIO pins by default. These need to be disabled in many cases, by configuring those
pins as high-impedance inputs.
Table 7
Pin direction and pullup control
Shield
pin
Output enable GPIO (high = output)
Pullup enable GPIO
Pin
Linux
Power-on default
1
Pin
Linux
Power-on default
2
IO0
U34_ IO0.0
248
Pulled-down input
U39_IO0.0
216
Pulled up input
IO1
U34_ IO0.1
249
Pulled-down input
U39_IO0.0
217
Pulled up input
IO2
U34_ IO0.2
250
Pulled-down input
U39_IO0.0
218
Pulled up input
IO3
U34_ IO0.3
251
Pulled-down input
U39_IO0.0
219
Pulled up input
IO4
U34_ IO0.4
252
Pulled-down input
U39_IO0.0
220
Pulled up input
IO5
U34_ IO0.5
253
Pulled-down input
U39_IO0.0
221
Pulled up input
IO6
U34_ IO0.6
254
Pulled-down input
U39_IO0.0
222
Pulled up input
IO7
U34_ IO0.7
255
Pulled-down input
U39_IO0.7
223
Pulled up input
IO8
U34_ IO1.0
256
Pulled-down input
U39_IO0.7
224
Pulled up input
IO9
U34_ IO1.1
257
Pulled-down input
U39_IO0.7
225
Pulled up input
IO10
U34_ IO1.2
258
Pulled-down input
U39_IO0.7
226
Pulled up input
IO11
U34_ IO1.3
259
Pulled-down input
U39_IO0.7
227
Pulled up input
IO12
U34_ IO1.4
260
Pulled-down input
U39_IO0.7
228
Pulled up input
IO13
U34_ IO1.5
261
Pulled-down input
U39_IO0.7
229
Pulled up input
IO14
U16_ IO0.0
232
Pulled-down input
U17_ IO1.0
208
Pulled up input
IO15
U16_ IO0.1
233
Pulled-down input
U17_ IO1.1
209
Pulled up input
IO16
U16_ IO0.2
234
Pulled-down input
U17_ IO1.2
210
Pulled up input
IO17
U16_ IO0.3
235
Pulled-down input
U17_ IO1.3
211
Pulled up input
IO18
U16_ IO0.4
236
Pulled-down input
U17_ IO1.4
212
Pulled up input
IO19
U16_ IO0.5
237
Pulled-down input
U17_ IO1.5
213
Pulled up input
1
These pins are externally pulled down inputs at power-on. This effectively selects input direction for level shifters.
2 These pins are internally pulled up inputs at power-on. This effectively enables pullups (as 100 kohm + 47 kohm in series).
§
Intel® Edison Kit for Arduino*
Hardware Guide
December 2014
12
Document Number: 331191-004