NXP Semiconductors

UM11597

PCF2131-ARD evaluation board

4.5 I2C/SPI bus selection

The PCF2131TF can interface with an SPI or I2C interface. While SPI interface is

selected, install jumpers on J2 across pins 1&2, 3&4, 5&6, 7&8, 9&10. While I2C interface

is selected, install jumpers on J1 across pins 1&2, 3&4, 5&6, 7&8, 9&10. Placing a

jumper across pins 1&2 on J1 or J2 shorts the IFS pin to either VDD (to select I2C

interface) or GND (to select SPI interface).

J3 selects the I2C-bus source from Arduino interface (pins 9 and 10, connector J12, or

pins 5 and 6, connector J6).

aaa-043564

J1

J2

OPEN

CLOSE

CLOSE

OPEN

I2C

SPI

CLOSE for I2C

Interface

CLOSE for SPI

Interface

Add Jumpers to

isolate pull up

resistors from 3.3V

power

Change IFS

connection to

PCFVDD or VBBS

PCFVDD

VBBS

VDD_3V3

PCFVDD

VBBS

R12

0

J2

HDR_2X7

JUMPER(DEFAULT) = 1-2, 3-4, 5-6, 7-8, 9-10: OFF

JUMPER(OPTION1) = 1-2, 3-4, 5-6, 7-8, 9-10: ON - SPI-bus active

1

2

3

4

5

6

7

8

9

10

11

12

13

14

R2

10K

J1

HDR_2X7

JUMPER(DEFAULT) = 1-2, 3-4, 5-6, 7-8, 9-10: ON - I2C-bus active

JUMPER(OPTION1) = 1-2, 3-4, 5-6, 7-8, 9-10: OFF

1

2

3

4

5

6

7

8

9

10

11

12

13

14

R1

10K

R13

0

DNP

R4

10K

J15

HDR_2X4

JUMPER(DEFAULT) = 1-2, 3-4, 5-6, 7-8: ON - Pull-up res. connected

JUMPER(OPTION1) = 1-2, 3-4, 5-6, 7-8: OFF - Pull-up res. disconnected

1

2

3

4

6

5

7

8

U1

PCF2131

IFS

1

SCL

2

SDI

3

SDO

4

SDA/CE

5

INTA

13

INTB

12

VSS

7

GND

17

CLKOUT

6

TS1

8

TS2

9

TS3

10

TS4

11

BBS

14

VDD

15

VBAT

16

C1

0.1uF

R3

10K

J10

HDR 2X5

1

2

3

4

6

5

7

8

9

10

R11

0

C2

0.1uF

PCFVDD

PCFBAT

VBBS

I2C_SCL

I2C_SDA

I2C_INTA

I2C_INTB

PCF_IFS

SPI_SCK

PCF_SCL

SPI_MOSI

PCF_SDI

SPI_MISO

PCF_SDO

SPI_CE

PCF_SDA

SPI_INTA

SPI_INTB

PCF_INTA

PCF_INTB

CLKOUT

TS1

TS2

TS3

TS4

Figure 2. PCF2131-ARD daughterboard, I2C/SPI bus jumper selection

Note that interface selection should be done before the battery is supplied to VBAT

pin. Once VBAT pin is powered, interface type can’t be changed even with the jumpers

moved from I2C locations to SPI locations, or vice versa. To select a new interface type:

1. Remove power supply to the evaluation board, and disconnect the VBAT pin from

battery power by removing the jumper across J9.3&4, and placing a jumper across

J9.1&2

2. Change Interface Jumpers to either SPI (J2) or I2C (J1)

3. Connect VBAT pin to battery power (remove the jumper across J9.1&2, and place a

jumper across J9.3&4), and power the evaluation board again.

J4 (Aardvark) I2C

J12 (Arduino) I2C

J4 (Aardvark) SPI

J12 (Arduino) SPI

J1

Jumpers

J2

Jumpers

J1

Jumpers

J2

Jumpers

J1

Jumpers

J2

Jumpers

J1

Jumpers

J2

Jumpers

J1 J2

Jumper

Settings

❶=❷

❸=❹

❺=❻

❼=❽

❾=❿

⓫=⓬

⓭=⓮

① ②

③ ④

⑤ ⑥

⑦ ⑧

⑨ ⑩

⑪ ⑫

⑬ ⑭

❶=❷

❸=❹

❺=❻

❼=❽

❾=❿

⑪ ⑫

⑬ ⑭

① ②

③ ④

⑤ ⑥

⑦ ⑧

⑨ ⑩

⑪ ⑫

⑬ ⑭

① ②

③ ④

⑤ ⑥

⑦ ⑧

⑨ ⑩

⑪ ⑫

⑬ ⑭

❶=❷

❸=❹

❺=❻

❼=❽

❾=❿

⓫=⓬

⓭=⓮

① ②

③ ④

⑤ ⑥

⑦ ⑧

⑨ ⑩

⑪ ⑫

⑬ ⑭

❶=❷

❸=❹

❺=❻

❼=❽

❾=❿

⑪ ⑫

⑬ ⑭

Table 2. I2C/SPI bus selection

UM11597

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© NXP B.V. 2021. All rights reserved.

User manual

Rev. 1.0 — 15 September 2021

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