Interfacing an External I2C Device with the CYUSBS234/236 DVK – KBA91299

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    Question: How can you connect an external I2C device to the CYUSBS234/236 DVK?

     

    Answer:

    The CYUSBS234 development kit (DVK) has one serial communication block (SCB) that can be configured as I2C. The CYUSBS236 DVK has two SCBs (SCB0 and SCB1) that can be configured as I2C. By default, the I2C lines of the SCBs on both of the DVKs are connected to the on-board EEPROM(s) through jumpers (J17 and J20 for CYUSBS234; J17, J20, J24 and J25 for CYUSBS236). The I2C pins for SCB0 and SCB1 are available on the development board jumpers. The following table provides the details on the locations of the I2C pins available on both of the DVKs.

    Table 1. I2C Pin Mapping

                                                                                                                                                     
             CYUSBS234    CYUSBS236
             SCB    SCB0    SCB1
             On Board
        EEPROM
        External I2C device    On Board
        EEPROM
        External I2C
        device
        On Board
        EEPROM
        External I2C
        device
        SCL    Short Pin No:2
        and 3 of J17
        Remove the short
        present on J17.
        Connect the SCL
        line of the external
        I2C device to
        Pin No: 2 of J17
        Short Pin No:2
        and 3 of J17
        Remove the short
        present on J17.
        Connect the SCL
        line of the external
        I2C device to
        Pin No: 2 of J17
        Short Pin No:2
        and 3 of J24
        Remove the short
        present on J24.
        Connect the SCL
        line of the external
        I2C device to
        Pin No: 2 of J24
        SDA    Short Pin No:2
        and 3 of J20
        Remove the short
        present on J20.
        Connect the SDA
        line of the external
        I2C device to
        Pin No: 2 of J20
        Short Pin No:2
        and 3 of J20
        Remove the short
        present on J20.
        Connect the SDA
        line of the external
        I2C device to
        Pin No: 2 of J20
        Short Pin No:2
        and 3 of J25
        Remove the short
        present on J25.
        Connect the SDA
        line of the external
        I2C device to
        Pin No: 2 of J25

    You can connect the SCL and SDA lines of the external device to the pin numbers shown in Table 1.

    Please note that the pull-up resistors on the I2C bus are connected nearer to the on-board I2C EEPROM (as shown in Figure 1) and hence will get disconnected when the jumper shortings are removed. When you interface an external I2C device to the CYUSBS234/236 DVK, ensure that the pull-up resistors are present on the I2C lines of the external device.

    Figure 1. I2C Connection