What is the SWD driver impedance of SWDIO line?

RE: What is the SWD driver impedance of SWDIO line?

onurcanbaysal — Thu, 13 Apr 2023 09:25:21 GMT

Can you kindly provide any document for our reference ?

RE: What is the SWD driver impedance of SWDIO line?

godmode — Sat, 27 Feb 2021 10:57:13 GMT

RE: What is the SWD driver impedance of SWDIO line?

LRa — Fri, 26 Feb 2021 18:44:12 GMT

This is exactly what i am trying to build to hook up several PCBs to one Debugger for testing purposes.

Are you willing to share some more details (maybe schematics?)

I guess the power supply to the target is not provided via the multiplexer board?

RE: What is the SWD driver impedance of SWDIO line?

Supriya Barigela — Fri, 28 Feb 2020 06:30:01 GMT

Hi sir,

I'm unable to contact you. Please provide your mail or contact number.

(send through PM)

RE: What is the SWD driver impedance of SWDIO line?

godmode — Wed, 19 Feb 2020 08:10:39 GMT

PM = I have sent you a Private Message

RE: What is the SWD driver impedance of SWDIO line?

Supriya Barigela — Wed, 19 Feb 2020 07:48:08 GMT

Sorry I didn't understand.

What is PM?

Can you provide your design?

RE: What is the SWD driver impedance of SWDIO line?

godmode — Wed, 19 Feb 2020 06:06:42 GMT

RE: What is the SWD driver impedance of SWDIO line?

Supriya Barigela — Wed, 19 Feb 2020 04:19:20 GMT

like your hardware schematic for our reference.

RE: What is the SWD driver impedance of SWDIO line?

godmode — Tue, 18 Feb 2020 11:17:53 GMT

What reference do you need?

RE: What is the SWD driver impedance of SWDIO line?

Supriya Barigela — Tue, 18 Feb 2020 09:36:26 GMT

we are developing SWD multiplexing for 16 devices.

Please provide any document for our reference.

RE: What is the SWD driver impedance of SWDIO line?

jsantosrico — Wed, 03 Apr 2019 13:43:21 GMT

Hi, I'm in a similar situation. I will get into production of a medium size batch and need to do something like you did. I was wondering if you could share more info about your multiplexer board. I sent you a private message in case you can't publicly give more info about it.

Thanks!

RE: What is the SWD driver impedance of SWDIO line?

godmode — Tue, 26 Mar 2019 16:22:21 GMT

I have replied to your PM :)

RE: What is the SWD driver impedance of SWDIO line?

Dimitar — Tue, 26 Mar 2019 14:15:32 GMT

It passed a six months, and I simply missed you answered me. Do you continue using this multiplexer and script/software for it further? I try to send a PM, but I don't know if you have chance to read it.

RE: What is the SWD driver impedance of SWDIO line?

Dimitar — Mon, 24 Sep 2018 09:10:02 GMT

Will check the setup tomorrow and come back.

RE: What is the SWD driver impedance of SWDIO line?

godmode — Mon, 24 Sep 2018 08:52:10 GMT

VREF is voltage reference of target board. It is needed so the programmer/debugger can properly align the voltage signals. In your setup you need to connect pin 1 (EXT_VTG) of P19 on dev.kit to VREF. Im sure you are using P19 to programm your boards?
JLink is one of the fastest of programmers on the market and in a fact a standard at the time.
For the JLink we are suppling the automation scripts. If you are going to use the dev.kit you need to provide your own scripts or switch between the boards manually by the terminal application (cables are all connected no switching needed).

RE: What is the SWD driver impedance of SWDIO line?

Dimitar — Mon, 24 Sep 2018 08:28:01 GMT

Currently I am using nRF52 dev.kit to program the boards, and have only 2 program plus 2 power pins.

J-link can be an option, if that will make it faster and problem free, otherwise no need for it. Of course program chips at HiLo is may be easiest, but there should be some fun, too.

RE: What is the SWD driver impedance of SWDIO line?

godmode — Sat, 22 Sep 2018 10:56:02 GMT

Hi Dimitar,

I will ask at my place are they going it to sell it or not and let you know on private message.

Are you going to use JLink? If so they you need the VREF.

RE: What is the SWD driver impedance of SWDIO line?

Dimitar — Sat, 22 Sep 2018 09:58:01 GMT

Hi @godmode, looks like really nice programming setup. I probably need something like for a panel of 20x nRF51822.

Choice is between 20x standalone programmers with memory and common trigger, or something like your setup.

Using 20x nRF52 dev boards seems not a nice solution :)

Are you going to sell this as commercial product, as kit or publish the hardware/software design? In my case VREF is not needed, I think.

Thanks in advance!

RE: What is the SWD driver impedance of SWDIO line?

godmode — Wed, 04 Jul 2018 09:32:22 GMT

Thank you.
I have used Texas Instruments SN74CB3Q3251.
You are looking for analog multiplexer/demultiplexer.

RE: What is the SWD driver impedance of SWDIO line?

servus — Wed, 04 Jul 2018 08:47:14 GMT

Hi, your multiplexer board looks very nice. Can you pls tell me, which multiplexer IC you have used?

thanks.

RE: What is the SWD driver impedance of SWDIO line?

godmode — Sat, 30 Jun 2018 08:11:47 GMT

Thank you for all your help.
I have SWD multiplexer fully functional.
We are very happy everything is working because without JTAG support multiplexer like this is the only way to debug or flash multiple devices.
Below I have put some photos :)

It has 48 ports which multiplexes three SWD signals: VREF, SWDIO, SWCLK. GND is common.
We are using it for production: programming 40 devices takes 2 minutes at 4MHz JLink's clock,
and debugging: hardware is connected to PC and VPN, anytime we find a glitch it is possible to debug a device remotely without changing the cables.
Cables are 250cm long.
Multiplexer is controlled by scripts or standalone GUI application.

drive.google.com/folderview

RE: What is the SWD driver impedance of SWDIO line?

Kenneth — Wed, 06 Jun 2018 12:04:02 GMT

Thanks for the clarification, I just wanted to make sure.

Best regards,
Kenneth

RE: What is the SWD driver impedance of SWDIO line?

godmode — Wed, 06 Jun 2018 08:34:01 GMT

I do not want to program many chips in parallel - I want to multiplex one debugger to many devices. It will program one at a time but without disconnecting cable from Device(n) to Device(n+1) and so on.
After one device is done mutiplexers are switched are switched to another device. Always only one device is connected to debugger.

Thank you for your help!

RE: What is the SWD driver impedance of SWDIO line?

Kenneth — Wed, 06 Jun 2018 08:26:09 GMT

We have not seen long cables to be a problem, and our own lab we have similar setup (very long cables in some cases). The input is very high impedance, the output is very low impedance. You can find some data in our datasheet in terms of rise and fall times with a regular GPIO (SWDIO can be considered a GPIO configured in low drive mode in those tables):
http://infocenter.nordicsemi.com/topic/com.nordic.infocenter.nrf52832.ps.v1.1/gpio.html?cp=2_1_0_19_3#unique_1820404704

Note that we do not recommend a setup where you try to program many chips in parallel, and only readback/verify on possible 1 chip. We have seen similar attempts before, and in those cases there have been various issues, for instance the timing will be controlled by the 1 you actually verify.

RE: What is the SWD driver impedance of SWDIO line?

godmode — Tue, 05 Jun 2018 13:10:21 GMT

Actually I need to know what is the output impedance of SWDIO to do impedance matching for long cables (suppress signal reflection)?