Opentx: crossfireTelemetryPush function cause emergency mode on T16

[lichtl]

Describe the bug
crossfireTelemetryPush function cause to crash openTX 2.3.5 (T16 will go into emergency mode / X9D will not properly execute function) when send 23 byte.

To Reproduce
Steps to reproduce the behavior:

1. Add/setup model with external Crossfire (no module required)
2. Add following lua on the SD card

local function run(event)
    lcd.clear()
    if event == EVT_ENTER_LONG then
        lcd.drawText(10, 20, "23 byte - PID change", 0)
        local result = crossfireTelemetryPush(0x78, {234,200,67,18,11,184,0,35,39,16,11,184,0,35,39,16,31,64,0,50,19,136,135})
        lcd.drawText(10, 35, "done", 0)
    end
    return 0
end

return { run=run }

1. Launch lua and hold ENTER key to trigger (T16 will go into emergency mode / X9D will not send out command) - https://youtu.be/ImHcW7YLh1A

Expected behavior
Command should be executed and send to Crossfire module

General information

• OpenTX version (2.3.4 and 2.3.5 tested)
• Hardware (Frsky X9D+, Jumper T16 both tested.)

[3djc]

Anything above 16 (the size of the buffer) will get you into trouble I think. Will double check with TBS, and add a safety mechanism

[fedorcomander]

TBS packet is up to 64 bytes. It was ok on OTX 2.2.

[3djc]

If you where sending 64 bytes in 2.2, you where probably massively exceeding buffer size (#define TELEMETRY_OUTPUT_FIFO_SIZE 16)

[fedorcomander]

Great… Well… There are specs for crossfire protocol, and buffer must be extended to 64 bytes. Sorry.

On 20 Jan 2020, at 09:08, 3djc [e-mail] wrote:

If you where sending 64 bytes in 2.2, you where probably massively exceeding buffer size (#define TELEMETRY_OUTPUT_FIFO_SIZE 16)

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[3djc]

Not sure we have the memory available for that, we will have a look, not commiting to that

[fedorcomander]

Well, telemetry receiving buffer is 256 bytes if i am not mistaken. which is quite a lot. can be smaller? ;)

[kilrah]

We can't control when we receive stuff, but we can control when we send stuff. Normal to have RX bigger.

[fedorcomander]

Yes, thats true. But specs are specs.

Meanwhile, i patched device.lua so it will work with float numbers that kiss uses a lot. That DOESNT let you guys off the hook with buffer size ;)

[syrekszymon]

...Meanwhile, i patched device.lua ...

Where can i find it?

[AngusCox]

...Meanwhile, i patched device.lua ...

Where can i find it?

Here, https://www.patreon.com/posts/33299763

[3djc]

We will extend the buffer to 64 and put safeguards

[fedorcomander]

perfect! thank you from all kiss users.