About Fast-GPIO

Reply to About Fast-GPIO on Sat, 22 Dec 2018 13:20:08 GMT

Gnichi Mohamed — Sat, 22 Dec 2018 13:20:08 GMT

Hi guys,
In the fast-gpio repository opening /dev/mem is executed in the Module::_SetupAddress.
After opening /dev/mem the close(m_mfd) function is called which closes /dev/mem before doing any write command.
I am trying to toggle gpio15 in my C++ program and its not working yet.

Reply to About Fast-GPIO on Sat, 22 Dec 2018 14:43:19 GMT

Maximilian Gerhardt — Sat, 22 Dec 2018 14:43:19 GMT

In https://github.com/OnionIoT/fast-gpio/blob/master/src/fastgpioomega2.cpp, the FastGpioOmega2() constructor calls _SetupAddress(REG_BLOCK_ADDR, REG_BLOCK_SIZE); which open("/dev/mem", O_RDWR), then mmaps 1024 bytes starting from the given base address. The result tof the mmap is stored into regAddress and based on this memory-mapped address the program accesses the registers. So the file handle is not needed anymore and is closed.

The mmap-ed block should later freed using munmap() but the code doesn't do that. However, it should still work.

I.e. I don't see a problem with the library code. What is the application program you've written to access GPIO15?

Reply to About Fast-GPIO on Mon, 24 Dec 2018 08:03:09 GMT

Gnichi Mohamed — Mon, 24 Dec 2018 08:03:09 GMT

@Maximilian-Gerhardt Thank you for your reply.
GPIO16 and GPIO17 work on the Expansion dock but GPIO15 is always at 1.5V. I tested the same program on another MT7688 module but the same issue persists.
I am using openwrt 18.06 for the onion omega.

Reply to About Fast-GPIO on Wed, 26 Dec 2018 07:01:06 GMT

György Farkas — Wed, 26 Dec 2018 07:01:06 GMT

@Gnichi-Mohamed said in About Fast-GPIO:

GPIO16 and GPIO17 work on the Expansion dock but GPIO15 is always at 1.5V.

Omega-Expansion-Dock.pdf (IO is GPIO).

Forget what I wrote. I misunderstood your post(s).