TX28

PINOUT

Marked yellow: Not connected

PIN

Type

Function

i.MX28 Pad Name

Alternate functions

GPIO

Description (refer to i.MX28 manuals for details)

POWER SUPPLY & RESET

1-4

power VIN

Module power supply input (3.0V-5.5V)

5-7,

9-12

power VOUT

3.3V power supply output (up to 0.2A)

8

3V3

BOOTMODE

47K-PU

Boot mode select H: Boot from NAND / L: Boot from UART/USB

13

power VBACKUP

-

DS1339 RTC backup power supply. Supply voltage must be held

between 1.3V and 3.7V for proper RTC operation. This pin can be

connected to a primary cell such as a lithium button cell.

Additionally, this pin can be connected to a rechargeable cell or a

super cap when used with the trickle charge feature.

14

special

PSWITCH

100K-PU

47K-PD

10K series

Used for chip power on or recovery. PSWITCH is at MID LEVEL &

STARTUP by default. A 10kΩ resistor in series is used.

Connect to GND for LOW LEVEL, connect to 3V3 for HIGH LEVEL,

leave unconnected (MID LEVEL) if not used.

=> i.MX28 Reference manual chap 11.4 “PSWITCH Pin Functions”

15

3V3

FEC_RESET_B

ENET0_RX_CLK

ENET0_RX_ER

ENET0_1588_EVENT2_IN

GPIO4_13

10K-PU

Ethernet PHY reset – active low output signal. This pin is hard wired

to the onboard Ethernet PHY and provides a fixed function.

16

VIN

#POR

10K-PU

Power On Reset - active low input signal. Typically a push button

reset. Leave unconnected if not used. The i.MX28 is a PMU and an

SoC, power-on reset is generated internally. If low the power supply

connected to the i.MX28 is turned off.

17

3V3

#RESETIN

RESETN

This pin resets the chip if it is low. This pin is pulled up to VDDIO33

with an internal resistor. No external pull up resistors are needed

18

GND

GND

Ethernet

19

analog ETN_TXN

Transmit Data Negative: 100Base-TX or 10Base-T differential

transmit output to magnetics.

20

3V3

#ETN_LED2

Active low - output is driven active when the operating speed is

100Mbps. This LED will go inactive when the operating speed is

10Mbps or during line isolation.

21

analog ETN_TXP

Transmit Data Positive: 100Base-TX or 10Base-T differential transmit

output to magnetics.

22

power ETN_3V3

+3.3V analog power supply output to magnetics

23

analog ETN_RXN

Receive Data Negative: 100Base-TX or 10Base-T differential receive

input from magnetics.

24

3V3

#ETN_LED1

Active low - output is driven active whenever the device detects a

valid link, and blinks indicating activity.

25

analog ETN_RXP

Receive Data Positive: 100Base-TX or 10Base-T differential receive

input from magnetics.

26

GND

GND

USB-HOST

27

3V3

USBH_VBUSEN

SPDIF

ENET1_RX_ER

GPIO3_27 Active high external 5V supply enable. This pin is used to enable the

external VBUS power supply.

28

3V3

#USBH_OC

JTAG_RTCK

GPIO4_20

47K-PU

Active low over-current indicator input connected to a GPIO.

29

analog USBH_DM

USB1DM

D- pin of the USB cable

30

NC

not connected

31

analog USBH_DP

USB1DP

D+ pin of the USB cable

32

GND

GND

33

3V3

USBOTG_ID

USB0ID

PWM2

USB1_OVERCURRENT

GPIO3_18

ID pin of the USB cable. For an A-Device ID is grounded. For a B-

Device ID is floated.

34

3V3

USBOTG_VBUSEN

GPMI_CE2N

CAN1_TX

ENET0_RX_ER

GPIO0_18

Active high external 5V supply enable. This pin is used to enable the

external VBUS power supply.

35

analog USBOTG_DM

USB0DM

D- pin of the USB cable

36

3V3

#USBOTG_OC

GPMI_CE3N

CAN1_RX

SAIF1_MCLK

GPIO0_19

47K-PU

Active low over-current indicator input connected to a GPIO. 10kΩ

pull-up resistor.

37

analog USBOTG_DP

USB0DP

D+ pin of the USB cable

38

power USBOTG_VBUS

VDD5V

39

GND

GND

I2C

40

3V3

I2C_DATA

I2C0_SDA

TIMROT_ROTARYB

DUART_TX

GPIO3_25

1K-PU

I2C Data

41

3V3

I2C_CLK

I2C0_SCL

TIMROT_ROTARYA

DUART_RX

GPIO3_24

10K-PU

I2C Clock

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www.karo-electronics.de