topic Re: Link2 High and Low in LPC Microcontrollers

Link2 High and Low

leechen — Thu, 10 May 2018 03:15:49 GMT

For Link2, there are SWCLK and SWDIO, what's the threshold for high and low?

Re: Link2 High and Low

kerryzhou — Fri, 11 May 2018 07:04:06 GMT

Hello Lee,

LPC-LINK2 chip is the LPC4370, so you can refer to the LPC4370 datasheet:

High: need to >=0.7*VDD

Low: need to <=0.3*VDD

Wish it helps you!

If you still have question about it, please kindly let me know!

Have a great day,
Kerry

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Re: Link2 High and Low

leechen — Mon, 14 May 2018 03:35:09 GMT

Thank you Kerry.

What happened to me is that my customer's system had Vdd of 2.9V, and I had no problem to program it with Link2. However, after they changed the Vdd to 3.4V, I couldn't program with Link2. Do you know what might be the cause?

Re: Link2 High and Low

kerryzhou — Mon, 14 May 2018 08:24:22 GMT

Hi Lee,

What do you mean when changed the VDD to 3.4V? Do you mean, when LPC-LINK2 powered with the VDD with 3.4V, or your target board charged with 3.4V?

Please tell me what the target board you are using? and also give me more details, what the LINK2 board you are using? The lpcxpresso board or the LPC-LINK2 board?

Please give the detail information and steps how to reproduce the customer's problem, it's better to use the NXP official board.

Have a great day,
Kerry

Re: Link2 High and Low

leechen — Mon, 14 May 2018 10:24:39 GMT

Hi Kerry,

I use LPC-Link2. They use NXP LPC11u68 board. I couldn’t go into the debug mode, and the only difference they made on that board is that the Vdd was 2.9V, but now it has become 3.4V.

Re: Link2 High and Low

kerryzhou — Tue, 15 May 2018 02:29:29 GMT

Hi Lee,

Please tell me the LPC11U68 board full name if it is the official board, then I will also test it on my side.

Please tell me the detail step, how they connect, and how they modify the VDD to 3.4V, I need to review whether the customer's operation have some potential problems.

Just tell me the detail step to reproduce the problem, I will test it on my side.

If you use the LPC-LINK2, do you connect JP2? JP2 will power on the target board.

Have a great day,
Kerry

Re: Link2 High and Low

leechen — Tue, 15 May 2018 06:04:21 GMT

Hi Kerry,

They use their own board with MCU being LPC11u68. What’s weird is that one of their board has this problem, but there’s another board having no such problem. Maybe it’s defect on their board?

When I use Link2, I have JP1 disconnected, but JP2 connected. This is correct setting, right?

Re: Link2 High and Low

kerryzhou — Tue, 15 May 2018 08:35:19 GMT

Hi Lee,

Thank you for your updated information.

Please let the customer also tried the official board, whether they can reproduce the problem with different VDD.

If the official board can't reproduce it, I think maybe still need to check the customer's hardware.

About LPC-LINK2, your configuration is correct.

Have a great day,
Kerry

Re: Link2 High and Low

ianbenton — Tue, 12 Jun 2018 11:18:23 GMT

Aren't the important lines SWCLK and SWDIO buffered by a 74LVC2T45 between the LPC4370 and the connector? So, for the levels, shouldn't you be reading the 74LVC2T45 datasheet, not the LPC4370 datasheet?

http://www.ti.com/lit/ds/symlink/sn74lvc2t45.pdf

Boards that refuse to program for no apparent reason are quite common.

If you want reliable programming insert a buffer (74HC1G17) in the SWCLK line on the target board.

See https://community.nxp.com/message/952947 for details of my findings.