# mmapped GPIO registers

**URL:** <https://forums.developer.nvidia.com/t/mmapped-gpio-registers/59834>\
**Category:** Jetson TX2\
**Created:** [April 4, 2018, 12:32pm UTC](https://forums.developer.nvidia.com/t/mmapped-gpio-registers/59834 "2018-04-04T12:32:27Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![akmal.ali](https://sea2.discourse-cdn.com/nvidia/user_avatar/forums.developer.nvidia.com/akmal.ali/32/71763_2.png) [@akmal.ali](https://forums.developer.nvidia.com/u/akmal.ali)\
**Post date:** [April 4, 2018, 12:32pm UTC](https://forums.developer.nvidia.com/t/mmapped-gpio-registers/59834/1 "2018-04-04T12:32:27Z")

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Moving from TX1 to TX2 on a custom board. I am programming the FPGA on the board, by writing directly to a set of gpio pins. I open /dev/mem and mmap the registers into userland and write to them directly. On the TX1, this process allows me to toggle a pin at ~16MHz. However on the TX2, I can only manage ~ 2 MHz. This seems unaffected by the processor speed and so I wonder if there is a change that causes this behaviour?

I am writing to GPIO\_CNF\_, GPIO\_OE, GPIO\_OUT, GPIO\_IN registers for the relevant pins. I have already hogged the pins in the kernel dtb file and can program the FPGA using these registers.

Akmal