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TPS65950 StartUp and I2C(?) issue

Konstantin Schmidt
Prodigy 60 points
Other Parts Discussed in Thread: AM3715, TPS65950

We have design a custom board with AM3715 and TPS65950, almost the same like Beagleboard XM.

What we see is exactly the power up sequence REGEN-> VIO -> VDD1 -> VDD2 -> VPLL1 -> 32KCLKOUT -> SYSEN -> CLKEN -> HFCLKOUT -> NRESPWRON -> NRESWARM (from OMAP). But we can't boot from MMC because the VDD_MMC1 is always low. I understand, that OMAP should configure the TPS65950 / VDD_MMC1 over I2C, but I2C bus is dead.

We tried to control the TPS65950 over I2c with I2C-Master (AARDVARK) from PC. To do so, we have removed the OMAP. But we din't see a valid I2C-start condition! The I2C_SCL goes low for few us (only one time), I2C_SDA goes low before SCL, but goes high after few ns -- this is wrong. This is not a start condition and looks to me like the  TPS65950 drives the I2C_SDA.

1 - I2C_SCL

2 - I2C SDA

 

 

 The question is, does we have a chance to control a TPS65950 over I2C?

The schematics are the same like beagleboard xm, so if we remove the OMAP we should be able to control  the TPS65950 over i2c?

We have the same behavior on 5 boards.

Does have anyone any idea, what we can do?

 

Konstantin

  • 0
    TI__Genius 15100 points

    After the device is active you can control it with any I2C controller if you have the correct slave address. I dont see any problem with this.

    MMC boot is working on Mistral EVM and the drivers are included in software. Can you check if you are using the correct sys_boot configuration. I dont know how this is done on OMAP. You can find out details about this from OMAP support. OMAP is able to write to PMIC to start the MMC LDO to support this type of boot.

    Also, check if you have correct pull-up on the SCL. It is surprising to see that SCL level is only 200mV.

     

  • 0 in reply to Gandhar Dighe
    Prodigy 60 points

    The SYS_BOOT configuration is right, but anyway -- the OMAP is removed -- the TSP is stand alone. We see VDD1, VDD2, VIO_1V8, VPLL1, so the TPS is active. But still no connection over i2c.

    The SCL level is 1.8V (10x Probe). The Pull-Ups are okay.

    We'll try to change the TPS659xx with other silicon revisions, maybe this is the hardware issue (transport damage or something others(?)).

    Konstantin

  • 0 in reply to Konstantin Schmidt
    Prodigy 60 points

    We tried new silicon revision TPS65950A2 instead of   TPS65950B, but unfortunately we have the same behavior -- we still don't have an access to TPS65950 over i2c. Does anybody have a standalone TPS65950  without an OMAP and could try to read or write the internal registers over i2c?

    Is i2c always active? (VDD1, VDD2, VINT and VPLL1 are okay). How do we check if TPS65950 in reset state or running well?

  • 0 in reply to Konstantin Schmidt
    Prodigy 60 points

    Now we can control the TPS over i2c! The problem was our i2c adapter, which can't handle the 1.8V (only 3.3V). We use voltage converter now and it works very well. We are able to access to TPS and switching the VMMC1 on. But anyway, the OMAP is still not starting, but this is not the PMU problem anymore.