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[Rahim Pardhan]

Rahim Pardhan

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• Super Hero
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Hello,

How can I access the GPIO and ADC pins on the 9260? I'm trying to interface a 3-axis accelerometer with the ADC and a bunch of limit switches to the GPIO. Any help is appreciated.

Regards,

Rahim

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The GPIO and ADC control registers are memory mapped and can be accessed directly from user space program.  The detailed information can be found in AT91SAM9260 user's manual.  There is an experimental GPIO driver posted in the forum.

[Rahim Pardhan]

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• Super Hero
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The experimental driver is not for the 9260? Can I still use this?

Thanks,

Rahim

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It only require minor modification (change GPIO line to the pins available on GESBC-9260) and recompile.

[Jerry Wong]

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• Super Hero
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We've been at this for hours and we still have nothing:

- After spending a lot of time figuring out the pinout, does J16 look like this (from top down):

1 2
3 4
5 6
...
47 48
49 50

This is the only numbering scheme in which things make sense for us, please confirm.

- We have implemented the experimental driver provided by Glomation for accessing GPIO. In both the driver as-provided and our own modified version, changing the value of a pin reports back successfully, but nothing happens on the J16 connector (the values do not change).

Can Glomation look in to this? This is a rather urgent problem for us, and it's disappointing that something as simple as GPIO doesn't work out of the box.

Here is a test output from our test app, for what it's worth:

Code:

GESBC:/GPIO# ./gpio-test.o                                                     
AT91_PIN_PB29 (TRIGGER) = 1                                                     
AT91_PIN_PB30 (RELOAD) = 1                                                     
AT91_PIN_PB31 (ZOOM) = 1                                                       
AT91_PIN_PC0 (SEG0_3) = 1                                                       
AT91_PIN_PC1 (SEG0_2) = 1                                                       
AT91_PIN_PC2 (SEG0_1) = 1                                                       
AT91_PIN_PC3 (SEG0_0) = 1                                                       
AT91_PIN_PC4 (SEG1_3) = 0                                                       
AT91_PIN_PC5 (SEG1_2) = 0                                                       
AT91_PIN_PC6 (SEG1_1) = 0                                                       
AT91_PIN_PC7 (SEG1_0) = 0                                                       
                                                                               
                                                                               
+PC4                                                                           
GESBC:/GPIO# ./gpio-test.o                                                     
AT91_PIN_PB29 (TRIGGER) = 1                                                     
AT91_PIN_PB30 (RELOAD) = 1                                                     
AT91_PIN_PB31 (ZOOM) = 1                                                       
AT91_PIN_PC0 (SEG0_3) = 1                                                       
AT91_PIN_PC1 (SEG0_2) = 1                                                       
AT91_PIN_PC2 (SEG0_1) = 1                                                       
AT91_PIN_PC3 (SEG0_0) = 1                                                       
AT91_PIN_PC4 (SEG1_3) = 0                                                       
AT91_PIN_PC5 (SEG1_2) = 0                                                       
AT91_PIN_PC6 (SEG1_1) = 0                                                       
AT91_PIN_PC7 (SEG1_0) = 0                                                       
                                                                               
                             

Between polls we tried changing PC4 to 1, which clearly does not work. Checking pins PC0 through PC7 is also confusing, as they definitely do not actually have voltages reflecting the 1,1,1,1,0,0,0,0 pattern as reported by the driver. All that aside, setting +PC0, +PC1, +PC2... etc do not seem to have any effect on the corresponding pins (all pins are zero in reality).

We have attached our driver code.

[edit] We have also alternatively tried using mmap to get GPIO working. We've attached the source for this as well. The mmap operation fails with (-EINVAL), but I simply cannot figure out what's wrong.

[admin]

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The pins on GPIO connector J16 is numbered as you indicated.

The GPIO will be supported by the next release of main line Linux kernel.

For quick testing you can use the following sequence of commands to check GPIO PC10,

devmem2 0xfffff800 w 0x400
devmem2 0xfffff810 w 0x400
devmem2 0xfffff830 w 0x400
sleep 5
devmem2 0xfffff834 w 0x400

devmem2 is a utility program that allows access of any memory location from user space.  The source code can be downloaded from http://free-electrons.com/pub/mirror/devmem2.c

Your pio-1.c program doesn't seem to reset the output value at correct register.  Please see above example.  Anothing you can try in your poi-1.c program is to toggle one output line with some sleep interval so you can connect a LED or meter to check the output voltage level change.

[Jerry Wong]

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• Super Hero
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Our PIO app doesn't even get that far It fails on mmap. Do you have any pointers on what we're doing wrong? It doesn't seem to want to map that address for us.

[admin]

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Please use devmem2 memory mapping as reference.

Try to change the memory mapping call to,

mem_page = mmap(0, MAP_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, PIO_C & ~MAP_MASK);