Px4-autopilot: Feature request: UART TX DMA

[ksschwabe]

Currently it looks like there is only UART DMA on the RX line.

We were trying to implement a "fast" file transfer via UART to a UART to Ethernet bridge and discovered that we were running into CPU usage issues. It looks to us that only the UART RX makes use of DMA. It should be a lot more computationally efficient to make use of the UART TX DMA as well for sending of large files.

Perhaps @dagar and @davids5 know more about the background working of the NuttX UART sending.

[mhkabir]

@bkueng @davids5

[davids5]

The issue is the DMA on the stm32 is to make up for a lack of RX FIFO in HW.
First Question is:If there are HW DMA resources available.
Then adding the same for the TX side will help to a point. But the real win is streaming DMA. This is only partially (incomplete) in Nuttx and would need some significant development effort.

[dagar]

Upstream NuttX pull request (that's stalled). https://bitbucket.org/nuttx/nuttx/pull-requests/858

[davids5]

@dagar I told Greg it is on my todo list during the H7 port. However we will just do the circular mode.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[mhkabir]

Go away

[julianoes]

Seriously, we can't all waste our time yelling at a bot.

[hamishwillee]

@julianoes SURE WE CAN :-)

[davids5]

F7 is in test now.

[davids5]

Up-streamed