Replacing LPC5534 to LPC5536 causes SWD connection issue

[Bobsaito]

Hello team,

I have a prototype board with LPC5534 on it. I can connect to MCU-Link Pro via SWD by clicking 'Debug' button on MCUExpresso IDE.
But when I try the same thing on the same board with LPC5536 on it, MCUExpresso IDE started complaining about missing SWD target.
I thought they are pin-to-pin compatible (LPC5534JBD100 and LPC5536JBD100) but it looks like that's not the case.
Then I stripped all unnecessary connection and just hooked power (MCUVDD), SWD (3 pins) and /RESET but MCUExpresso still kept throwing the same message.

Is there any pin(s) to be pulled up or pulled down upon boot/reset to let the MCU go into SWD mode?
Pulling-up/down the ISP0/ISP1 pins (or leave them open) didn't help.

Any information would be much appreciated.

[xiangjun_rong · Accepted solution]

Hi,

I have checked the data sheet of LPC553x, I suppose that difference for LPC5534JBD100 and LPC5536JBD100 is that the flash/RAM size, they are pin to pin compatible.

But if you populated LPC5534JBD100 on PCB, but you want to download LPC5536 project to the LPC5534, maybe there is issue, the probe may check the part number of the processor when it download.

If you replace the LPC5534JBD100 with LPC5536JBD100 on PCB, then download LPC5536 project, is it okay?

Hope it can help you

BR

XiangJun Rong

[Bobsaito]

Hello XiangJun,

It ended up that the device did not boot properly due to the floating GND pad.
After re-mounting the MCU, MCU-Link Pro could connect to it.

Thank you very much for your help.

Bobsaito