OMAP 35xx : How to setup GPIO pins as Input and read them?

IsaacLeung

Other Parts Discussed in Thread: SYSCONFIG, OMAP-L138

I'm trying to setup some GPIO pins as inputs so I can read some data from an external device. I can 'scope the pin and see I'm getting the correct value, but in my software (Linux app), it is not reading the value.

These are the steps I'm using to set up the GPIO

Configure pins as GPIO via the register that controls MUX mode
Setup the GPIO_SYSCONFIG register as appropriate for the individual GPIO modules that are in use
Setup the GPIO OE register. Actually by default, these are configured as INPUT so I should only need to do this for outputs
Set up the GPIO IRQENABLE1, IRQENABL2 and WAKEUP ENABLE registers (I assume write "1" to the appropriate bit).
Setup the GPIO LEVELDETECT0/LEVELDETECT1 registers

Is that it? I'm fairly confident Steps 1-3 are done correctly, as I have some pins set as OUTPUTS and I can see them toggling. TRM says I need to setup as in Step 4, so I assume just enable it. I have read-back these registers and verified that they are set as I think they should be.

However, when I query the GPIO_DATAIN register, I still do not get it registering the actual value that is on the pin. Am I missing anything?

over 16 years ago

0 Brad Griffis over 16 years ago

TI__Guru*** 125430 points

Is this your issue:

http://wiki.davincidsp.com/index.php/Additional_Configuration_for_GPIO120-129_on_OMAP35x

0 IsaacLeung over 16 years ago in reply to Brad Griffis

Intellectual 395 points

I will check to be sure, but it is probably not as I'm not using that range of GPIO.

Actually the exact GPIO I'm using are GPIO102, GPIO103, GPIO114, GPIO115 and GPIO170.

Is there some interface or functional clock register I have to set up for GPIOx modules (other than GPIO1)? I will look into that...

0 Brad Griffis over 16 years ago in reply to IsaacLeung

TI__Guru*** 125430 points

In the CONTROL_PADCONF_X register (where you set the mux mode) there is also an INPUTENABLE bit. Make sure you set it.

0 IsaacLeung over 16 years ago in reply to IsaacLeung

Intellectual 395 points

Here's some pseudocode for what I'm doing:

write(CONTROL_PADCONF_GPIO115_ADDR, 0x761C);
write(CONTROL_PADCONF_GPIO114_ADDR, 0x761C);
write(GPIO4_SYSCONFIG_ADDR, 0x00000015);
write(GPIO4_OE_ADDR, 0xFFFFFF3F); // This sets the outputs, so GPIO114,GPIO115 should be left as input
write(GPIO4_IRQENABLE1_ADDR, 0xFFF3FFFF);
write(GPIO4_IRQENABLE2_ADDR, 0xFFF3FFFF);
write(GPIO4_WAKEUPENABLE_ADDR, 0xFFF3FFFF);
write(GPIO4_LEVELDETECT0_ADDR, 0xFFF3FFFF);
write(GPIO4_LEVELDETECT1_ADDR, 0xFFF3FFFF);
write(GPIO4_FALLINGDETECT1_ADDR, 0xFFF3FFFF);
write(GPIO4_RISINGDETECT1_ADDR, 0xFFF3FFFF);
result = read(GPIO4_DATAIN_ADDR);

From TRM, my understanding is setting both LEVELDETECT0 & 1 will constantly enable the interrupt on this thing, which is what I want. Regarding my read/write routines, they work perfectly fine for read/write of any register, so I assume it works properly and there's nothing special about the DATAIN register.

0 Brad Griffis over 16 years ago in reply to IsaacLeung

TI__Guru*** 125430 points

I repeat, you must set INPUTENABLE in the PADCONF!

0 IsaacLeung over 16 years ago in reply to Brad Griffis

Intellectual 395 points

Whooops! Sorry, that was my intent all along. Looks like I had everything set up correctly, but just stupidly miscounted a bit position.

It does appear to work okay now.

Thanks!

0 Don Masin over 13 years ago in reply to IsaacLeung

Intellectual 580 points

Hi,

I'm using omap-l138 and wince 6.0. Where can I find protocol for configuring gpio pins and commands. I've looked and found only general information, but nothing that I can use to code. Info is spread out so many places, it's hard to find anything.

Thanks much. DM

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OMAP 35xx : How to setup GPIO pins as Input and read them?