ST-Link cable length

[Moritz1]

Hello,

does anyone know what the maximum cable length is for the ST-Link programmer (20-pole ribbon cable)?

Maybe someone has experience with this?

Is it possible to bridge longer distances, e.g. 50 metres? (not the USB cable, but the 20-pole ribbon cable).

[Pavel A.]

USB cable, with active extender. Ask in your local computer store.

[Moritz1]

Please read the question correctly.

I specifically asked for the length of the 20 pin ribbon cable. NOT the USB cable!

[Tesla DeLorean]

Not designed/buffered for 50m operation.​ Only a handful of pins used.

[Tesla DeLorean]

Need to rethink approach.

​

Y​ou can get Ethernet based JTAG pods, perhaps GDB Remote Server

[AScha.3]

>Is it possible to bridge longer distances, e.g. 50 metres?

yes, but only at a data rate, that makes debug useless.

so for useful debug speed keep stlink cable 10...50cm length and make long distance other way - as recommended .

[S.Ma]

It is easier to reach longer distance with differential pairs than using single ended signals. Physics.

Extend the USB cable if you can, SWD is like 3 wire SPI bus, its performance will always be inferior to USB. Signal integrity for noise and bit error rate.

[Moritz1]

I do not need to debug over this long wire. Its just for flashing the binary. High speed is also not needed. The flashing process can take 1 minute, this would not be a problem.

But the question is: Is it possible to slow down the ST-Link so that this will work?

[SHick.2]

Active USB cable extender. Consult your neighbourhood computer shop.

[AScha.3]

>But the question is: Is it possible to slow down the ST-Link so that this will work?

try it. 140Kb is lowest standard speed setting. obviously nobody had the silly idea, to flash/update something in another building with a spi-like connection over the street. It could work at a very unstable and unreliable state, most time errors will stop connection after some seconds. If you insist, to have a lottery game as update process, you will have a lot of fun.

use the internal bootloader or your own with local connection.

i use USB-stick, software just looking for update file on new/starting device and then update itself.

[Uwe Bonnes]

Use the bootloader and the serila connection for programming. Even slowing down SWD/JTAG may not help, as reflections can easily produce ghost edges that will get SWD/JTAG communication out of order. Otherwise series termination all signals at the source will lower reflections and additional ground line will reduce ground bounce.