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12437 Discussions

GPIO Driver/SysFS problem with Linux 3.16

Honored Contributor II

Good morning, 


We are facing a problem using Altera GPIO driver & SysFS on our system. 

Our design include: 

- A Nios2 processor running rel_socfpga-3.16_14.09.02 Linux version.  

- 1 Altera pio IP who handle 8 inputs 

- 1 Altera pio IP who handle 8 outputs 

- 1 Altera pio IP who handle 8 bidirectionnals signals 


We can export using SysFS all I/O off the design and drive out every output signal. 

However, we are able to read only one of the 8 input values. 

Same phenomenon for bidirectionnal signal after setting theire direction to input. 


Input values are always seen as '1'. 


For example: 

8 bidir set as input are exported from gpio248 to gpio255. 

All of them are connected to GND. 

Only gpio255 value is correct ( value = 0) 

The others values stay at 1. 


Does anyone knows this problem and a solution? 


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