ti8148 GPIO frequency problem

qiuxicj MESSN

Hi, all:

recently, I was testing the GPIO in TI8148, I would like to use the GPIO to output data in the rate about 500khz, but I follow the user guide of GPIO, found out that the GPIO data rate is only about 100hz. my test code is run in application program as following :

……

while(1){

system("echo 1 > /sys/class/gpio/gpio48/value");

system("echo 0 > /sys/class/gpio/gpio48/value");

}

……

Then， I test the output rate using oscilloscope is about 100 Hz only. I am confised. What is the highest data rate of the GPIO in TI8148？ Are there any other way to Use GPIO　in higher data rate？

BR,

qiuxicj

over 12 years ago

0 Steve Clynes over 12 years ago

TI__Mastermind 43875 points

Sysfs entries are an very slow mechanism and involve a lot of overhead. They are also very low priority so will not necessarily be processed quickly.

For a quicker update I would suggest using memory mapped register access to the GPIO registers directly.

BR,

Steve

0 qiuxicj MESSN over 12 years ago in reply to Steve Clynes

Intellectual 760 points

steve,

thank you for your reply.

I am a newer in this field, can you detail the way of "using memory mapped register access to the GPIO registers directly",or is there any user guide that I can reference.

thanks?

BR,

qiuxicj

0 Steve Clynes over 12 years ago in reply to qiuxicj MESSN

TI__Mastermind 43875 points

Please refer to the GPIO section of the TRM which should explain what memory addresses control the GPIO.

BR,

Steve

0 qiuxicj MESSN over 12 years ago in reply to Steve Clynes

Intellectual 760 points

Steve,

thank you so much!

I have solved the problem. I use ioremap() to map the physical addr to the virtual addr, and then I can access to the virtual addr using __raw_readl() and __raw_writel() directly .

BR,

qiuxicj

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ti8148 GPIO frequency problem