AM3359 - GPIO2_26 .. 31 not working (MMC0)

Felix Lembcke

Other Parts Discussed in Thread: AM3359

I just recently started working with CCS 6 as well as TI Sitara processors in general. I created a board which is quite similar in design to the IDK ICE2, and thus used the gel file provided with the ICE2 board to start with.

I can connect to the board and also change some of the pins via scripts in the GEL file. This works for all pins of the GPIO2 block except for GPIO2_26 .. 31 (the MMC0 pin group).

I selected the proper pinmux settings (the same as for GPIO2_0 .. 25).

It seems that I can't output values on these pins, and neither can I read incoming values (the external pins will always remain 0 and one of them with an external pull-up will remain high, but read as 0).

Thank You in advance for any help / suggestions.

over 11 years ago

0 Biser Gatchev-XID over 11 years ago

TI__Guru**** 393215 points

Hi Felix,

This forum supports only the Linux SDK for Sitara, however first thing you should check is whether the GPIO bank you are using has its functional clock enabled. See CM_PER_GPIO2_CLKCTRL register, bitfield MODULEMODE (AM335x TRM Rev. L, section 8.1.12.1.30)

0 Felix Lembcke over 11 years ago in reply to Biser Gatchev-XID

Prodigy 120 points

Yes, the module has it's clock turned on - all other pins of it (GPIO2_0 through GPIO2_25) work perfectly fine, I can toggle them and read them back (either if I drive them myself or if they are driven externally).

I wonder if I'm missing something due to the fact that all 6 pins have in common that their primary function is MMC0 (though I selected them to work as GPIO, just like all the others).

0 Biser Gatchev-XID over 11 years ago in reply to Felix Lembcke

TI__Guru**** 393215 points

Check if the pinmux doesn't get overwritten after you set it to GPIO.

0 Felix Lembcke over 11 years ago in reply to Biser Gatchev-XID

Prodigy 120 points

I checked and it seems that this is the issue (it seems that these pins are reverted back to their prior settings).

Any suggestions what could cause this? There are no other accesses to these registers withing the GEL file, as well as the program running on the AM3359 is just "Hello World" and is stopped (Due to JTAG access / breakpoint reached).
Could the hardcoded bootloader be responsible for this?

0 Biser Gatchev-XID over 11 years ago in reply to Felix Lembcke

TI__Guru**** 393215 points

Yes, I forgot to mention that. If MMC0 is included in your SYSBOOT settings the ROM code will initialize these pins.

0 Felix Lembcke over 11 years ago in reply to Biser Gatchev-XID

Prodigy 120 points

I believe these pins will become available after a valid image has been found, but is there a way to free these pins from their configuration due to SYSBOOT settings (other than changing the external SYSBOOT configuration)?

Thank You for Your Answers so far.

0 Biser Gatchev-XID over 11 years ago in reply to Felix Lembcke

TI__Guru**** 393215 points

Once you boot you can freely change the pinmux. However if MMC0 is included in the boot order before the actual device you boot from, they will always be initialized to MMC0 mode by the ROM code. If your boot device is before MMC0 they won't be changed from their default setting.

0 Felix Lembcke over 11 years ago in reply to Biser Gatchev-XID

Prodigy 120 points

So if I don't provide a valid image in one of the memories / peripherals defined in the boot chain (prior to MMC0) there is no proper way to use these pins (unless changing the boot chain which would require changes to the hardware), neither if I use a GEL file script, nor if I connect via JTAG and load a program (via JTAG from CCS)?
Is there no way to "unlock / use" these pins when accessing the device via JTAG?

0 Biser Gatchev-XID over 11 years ago in reply to Felix Lembcke

TI__Guru**** 393215 points

Yes you can, you simply have to write to the appropriate pad control registers. See sections 9.2.2, 9.3.1 and 9.3.1.49 of the AM335X TRM Rev. L for details.

0 Felix Lembcke over 11 years ago in reply to Biser Gatchev-XID

Prodigy 120 points

I've been trying that - both via GEL file script as well as within a program (loaded via JTAG) on the device, but reading back those registers after writing to them still yields their old value. So write access to these registers doesn't seem to work.

At the end of chapter 9.1 it says:
"For writing to the control module registers, the MPU will need to be in privileged mode of operation and writes will not work from user mode."

This is probably why I couldn't access (write to) any of the control module registers.
How can I change the mode of operation so that I can access them?

0 Biser Gatchev-XID over 11 years ago in reply to Felix Lembcke

TI__Guru**** 393215 points

I'm afraid I can't help much with CCS usage. You can try asking this on the Code Composer forum: https://e2e.ti.com/support/development_tools/code_composer_studio/f/81

0 Felix Lembcke over 11 years ago in reply to Felix Lembcke

Prodigy 120 points

It seems the issue was due to the GEL file - I used a different GEL file to start with (the one supplied together with the TMDSSK3358 Board), and it seems to work now.
Aside from that, it seems it was connected to the CPSR register.

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AM3359 - GPIO2_26 .. 31 not working (MMC0)