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The LPC55xx / LPC55Sxx is an Cortex-M33 based microcontroller for embedded applications including a Cortex-M33 co-processor.

Device recovery

In case some bad code has been flashed into the device (wrong PLL init that bricks the device, ...) that makes it unresponsive to debug commands, there is no built-in mechanism that allows J-Link to regain control over the device, however the device is not lost yet.

LPC55xx / LPC55Sxx series devices provide a specific pin to enter ISP mode on boot which effectively inhibits starting the user application and therefore the bad code. In order to recover an LPC55xx / LPC55Sxx series device that is running bad code, the following needs to be done:

  • Short PIO0_5 with GND
  • Power-cycle the device (make sure that LOW is sampled on PIO0_5)
  • Release PIO0_5
  • Start J-Link Commander, J-Flash or any other utility that supports J-Link and reflash the device

NOTE: On the LPC55S69-EVK there is a separate "ISP" button which can be used for this purpose.