GPIO 126 (mmc1_dat4) Problem using has output pin on OMAP3530

Stephane Grenier

Other Parts Discussed in Thread: OMAP3530, AM3703

We are running into a strange problem with GPIO pin 126 (P27, mmc1_data4) on an OMAP3530 chip. We are not able to use it has an output line to control a reset pin for our Ethernet chip on our board. The pin is set to low and does not want to be toggle to high. We try the internal Pull UP/DOWN but nothing works.

Here are the values in the associated registers on how we setup the pin:

CONTROL_PADCONF_MMC1_DAT4 (0x48002150) => 0x0118001c

GPIO4 (0x4905 4000):

GPIO_OE (0x4905 4034): 0xbffffffb

GPIO_DATAOUT (0x4905 403C): 0x40000000

In this configuration the pin is still set low event if the gpio_dataout register has been set to high.

We are able to toggle mmc1_data3, 2, 1 without any problems. Also we check the behavior of the pin on a Mistral board and we didn’t have the above issue. Is there an issue with this pin been use has a general io pin in a later revision of the silicon?

Base on the documentation, the pin should work has an Input/Ouput.

Ref #1: SPRS507F – February 2008 – Revised October 2009, Page 35, Ball Bottom P27

Ref #2: SPRUF98D – October 2009, Page 837, Table 7-5

Here are the Die ID’s for the two chips:

CDST: 229e00040000000004035c141001501e => GPIO 126 doesn’t work

Mistral: 446a00020000000004013e2a03015018 => GPIO 126 works

Any help would be appreciated,

Cheers and Thanks!

Steph

over 15 years ago

0 Brad Braun over 15 years ago

Prodigy 210 points

You may want to look at the input voltage connected to VDDS_MMC1A. If it's 1.8V, you need to configure the PBIAS settings appropriately for that voltage (the process is described in the OMAP TRM). I had a similar problem earlier this week on GPIO 128 (MMC1 DAT6).

0 Brad Griffis over 15 years ago in reply to Brad Braun

TI__Guru*** 125430 points

FYI, I wrote a wiki article on this very issue:

http://wiki.omap.com/index.php?title=Additional_Configuration_for_GPIO120-129_on_OMAP35x

I hope it helps. Basically it just goes into a little more detail on what Brad Braun just mentioned (thanks, Brad!).

0 Nathan Kro over 15 years ago

Intellectual 270 points

Steph

You should also note that some GPIOs can be found in more than one location on the OMAP35x processors. If two pins are set up for the same GPIO, it can have unwanted results.

Nate

0 Stephane Grenier over 15 years ago in reply to Brad Griffis

Prodigy 85 points

Thanks for the replies, I finally got around testing the suggestions, and I am still having issues with that pin (GPIO 126). After setting the following bits on the CONTROL_PBIAS_LITE register:

PBIASLITEVMODE1: 0 , need 1.8 Volt
PBIASLITEPWRDNZ1: 1, stable

The pin still doesn’t want to go high. What ever I do in the CONTROL_PADCONF_MMC1_DAT4 register, the pin stays low. I am at a lost here, any more suggestion here?

Cheers!

Steph

0 Brad Griffis over 15 years ago in reply to Stephane Grenier

TI__Guru*** 125430 points

What 32-bit value do you read at address 0x4800 2130? What 32-bit value do you read at 0x4800 2520?

0 Stephane Grenier over 15 years ago in reply to Brad Griffis

Prodigy 85 points

Brad,

Here are the value in the two registers:

1. 0x4800 2130: 0x000 0104

2. 0x4800 2520: 0x000 0201

Cheers!

Steph

0 Brad Griffis over 15 years ago in reply to Stephane Grenier

TI__Guru*** 125430 points

Looks like you're using the CBB package (0.4mm PoP) based on the pin numbers referenced. Please check pin P25 to verify 1.8V is applied.

0 Oren Rokach over 15 years ago in reply to Brad Griffis

Prodigy 180 points

Stephane,

we are encountering the same problem right now.

Did you solve this issue?

Thanks for you help

Oren.

0 Stephane Grenier over 15 years ago in reply to Oren Rokach

Prodigy 85 points

We did manage to resolve the issue.

We followed the instruction from Brad on the Wiki, but also I had to make sure to enable the vsim LDO power supply on the companion chip (4030) to 1.8V. The basic EVM setup doesn't enable it. After that was done everything worked like a charm.

Cheers!

Steph

0 Oren Rokach over 15 years ago in reply to Stephane Grenier

Prodigy 180 points

Thank you Steph

indeed it is workign for use as well

Thank you

Oren.

0 poov over 14 years ago in reply to Oren Rokach

Prodigy 10 points

In 37XX If I use just 4 bit MMC1 (120-125) I can then configure

If i use 126-129 as GPIO and actually get a 3volt tolerant GPIO on these 4 lines??

Iam finding difficult to comfigure.??

Thanks

RAM

0 Soren Steen Christensen over 14 years ago in reply to poov

Genius 3685 points

Hi RAM,

That would be possible. Please however take care. From the AM3703 TRM:

"CAUTION
Due to buffer strength, an external serial resistor must be connected to the balls corresponding to gpio_120 to gpio_129 pads. GPIO multiplexed on these pads should only be used with special electrical attention, and if no other solutions are possible for their considered application. They are not multiplexed on standard 1.8-V I/O cell buffers but specific dual-voltage USIM/MMC-compliant buffers with nonstandard voltage domains, power-up sequences, power states, and controls/configurations."

In case one know what one does I however see no problems using these 4 pins as 3V0 tolerant GPIOs...

Best regards - Good luck
Søren

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GPIO 126 (mmc1_dat4) Problem using has output pin on OMAP3530