USB DFU mode lost when Click on START on DFUsec tool after Reinvoke ISP

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by fred033 on Wed Oct 15 09:59:20 MST 2014

When I reinvoke ISP from my user code (using IAP command), my LPC4337 appear on computer and is detected by DFUSec.
I'm trying to flash a new firmware, but when I click on START on DFUsec tool, the DFU peripheral disappear and I have following log in DFUsec :

Downloading programming algorithm via DFU ROM boot
DFU programming algorithm download complete
Waiting Up to 4s for programming algorithm detection after DFU download
Board programming algorithm failed to start
Total program time:4.0232301 seconds.

I have tried to reinvoke ISP at the initialization of my software and all work fine. But when I reinvoke ISP when my software run the download is impossible.

To provoke the call of REinvoke ISP command I have done the following :
I send a VCOM command to my LPC (writing in a register)
When Core M0 detect this writting is send a command to M4 core and in this command treatment on M4 I reinvoke ISP.
On my computer my VCOM peripheral disappear and my LPC in DFU mode appear.
At this step I launch DFU SEC tool, and when I click on START to flash my board, the header seem to be download and after that my LPC in DFU disappear.   

I don't understand why.

Thank you for your help.