TWI and 11-bit I2C slave address devices

[tanekaf]

Hi. We are attempting to use the Infineon XMC1202 LED shield with our NRF52 device. The XMC1202 has an I2C address of 0x15E, instead of the traditional 7 bit address. We have been using the simple non-blocking TWI implementation to date. We can fake out the non-blocking TWI implementation for write commands. However for I2C reads, it is not clear how to pass in an address greater than 8 bits. Is this possible? Please advise.

[Jørgen Holmefjord]

Hi,

From the user manual of the shield I can see the following:

The RGB LED Shield’s I2C address is a 10-bit address and is pre-configured to be 0x15E. To address it, the master will send 2 bytes of address:

• The first 7 bits of the first byte are 11110XX, of which XX are the two most significant bytes of the 10-bit address. The 8th bit determines the read or write direction of the data transfer.
• The second byte is the lower 8-bits of the address.

This page describes the procedure for interfacing 10-bit addressable devices. If you setup a RXTX transfer where you write the second byte of the address before switching to TX mode, it should work. This is also described in section 3.1.11 in the I2C-bus specification and user manual.

Best regards,

Jørgen

[tanekaf]

Please disregard. Looks like we needed to enable TWI0_USE_EASY_DMA in our config file. That fixed the issue. Thanks again.