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

Version: **

 

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