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Original question:

TXS02326A: BSI input of TXS02326A

TXS02326A: Starting I2C interface for TXS02326A

Lyudmila Voronina
Intellectual 480 points
Part Number: TXS02326A
Other Parts Discussed in Thread: BQ25895

Hello

I 'm trying to start an I2C interface with the TXS02326A device but not yet successful.
TXS02326A and bq25895 are connected to I2C bus on our board.
The bq25895 device has the 0x6A address and answers on the i2cdetect utility request but
the TXS02326A device does not answer on the i2cdetect utility request.


Here is the result of the working i2cdetect utility (the i2cdetect utility from i2c-tools packet):
# ./i2cdetect -y 0                                                              
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f                             
00:          -- -- -- -- -- -- -- -- -- -- -- -- --                             
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --                             
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --                             
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --                             
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --                             
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --                             
60: -- -- -- -- -- -- -- -- -- -- 6a -- -- -- -- --                             
70: -- -- -- -- -- -- -- --

We see that the bq25895 device is defined and the TXS02326A device is undefined.
I checked all contacts - that's all right.
I soldered a new TXS02326A chip, but nothing has changed.
The SDA and SCK signals are pulled up through 10k to 3.3 V.

I have questions, help me:

1.
Is the Single Write and Single Read the same as on figure 21 and figure 22 for bq25895? (The
i2cReadWrite.png file for bq25895 is attached).

2.
The IRQ signal is involved in generating the TXS02326A device address.
We connect the IRQ input/otput directly to our processor and set the low level.
Then I set RSTX input to low level and then to high level. Then I run the i2cdetect utility.
Is it right? This sequence true?

I think there 's some  problem with forming an address here, but what I can 't understand.

Thanks in advance

  • 0
    TI__Genius 16725 points

    Hi,

    I am not sure how the I2C detect utility works. if IRQ is set to a 0 then to read from the device the address is 0x79 and to write the address is 0x78. Have you tried reading from this address?

    Thanks!

    -Karan

  • 0 in reply to Karan Kotadia
    Intellectual 480 points

    Hi, Karan

    The i2cdetect utility runs the 7 older bits of the address from 0x00 to 0x77 and adds the reading bit to the end, as shown in Figure 22.

    If the device answers, the i2cdetect utility displays 7 older bits of the device address.

    Our reading address is 0x79.  0x79 = slave address + read bit, as shown on Figure 22.

    0x79 = slave address + read bit  =  0111100 + 1  =>  slave address  = 0111100 = 0x3C.

    The i2cdetect utility would have to display the slave address, 7 higher bits excluding the lower reading bit, i.e. 0x3C.

    I am interested in  is reading/writing protocol for TXS02326A device similar to reading/writing protocol bq25895 device?

    I didn 't find any read/write diagrams in the internet for TXS02326A.

    Thanks.

  • 0 in reply to Karan Kotadia
    Intellectual 480 points

    Karan, in addition, I 'm sending a wiring circuit, maybe you 'll find errors. (txs02326a.JPG file attached)

    BSI input is open still, but I think it does not affect the I2C bus.

    IRQ is the input, as by default, interrupts are not allowed.

    We connect the OE input directly to our processor and set high level.
    I think the OE input does not affect the I2C bus, as by default OE is not
    used to control the data direction.

    The CLK input (pin 22) I set to high level, as we do not use
    еxternal clock source and by default internal clock source used.

  • 0 in reply to Lyudmila Voronina
    Guru 280390 points

    The i2cdetect utility starts a transaction and looks for the ACK, without actually reading or writing.

    If the capacitive load on the I²C lines is too high (check for proper rising edges with an oscilloscope), reducing the pull-up resistors would help.

    The datasheet says:

    • Power up the TXS02326A by asserting VBAT to enter the operation state
    • I²C Interface becomes active with the VDD_I/O supply

    Can you show the actual schematic with all components on the SDA/SCL lines?

  • 0 in reply to Clemens Ladisch
    Intellectual 480 points

    Hi, Clemens

    >> Power up the TXS02326A by asserting VBAT to enter the operation state

    I checked, VBAT = 3.3 V

    >> I²C Interface becomes active with the VDD_I/O supply

    I checked, VDD_I/O  =  3.3 V too.

    >>  Can you show the actual schematic with all components on the SDA/SCL lines?

    Only 2 devices TXS02326A and bq25895 are connected to I2C bus on our board. The bq25895 device has the 0x6A address and it answers on the i2cdetect utility request.

    >> If the capacitive load on the I²C lines is too high (check for proper rising edges with an oscilloscope), reducing the pull-up resistors would help.

    The SDA and SCK signals are pulled up through 10k to 3.3 V.

    I 'll look signals with an oscilloscope, thanks.

  • 0 in reply to Clemens Ladisch
    Intellectual 480 points

    Hi, Clemens

    The reason really was in the quality of I2C and SDA signals.

    I did not reduce the pull-up resistors, I just set up the I2C and SDA signals using IOMUX processor registers.

    Here is the result of the working i2cdetect utility (the i2cdetect utility from i2c-tools packet):

    # ./i2cdetect -y 0                                                              
         0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f                             
    00:          -- -- -- -- -- -- -- -- -- -- -- -- --                             
    10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --                             
    20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --                             
    30: -- -- -- -- -- -- -- -- -- -- -- -- 3c -- -- --                             
    40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --                             
    50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --                             
    60: -- -- -- -- -- -- -- -- -- -- 6a -- -- -- -- --                             
    70: -- -- -- -- -- -- -- --

    We see that the bq25895 device is defined and the TXS02326A device is defined too.

    Many thanks