[LPC1788] ISP autoboaud issue

[lpcware]

Content originally posted in LPCWare by pgr on Mon Mar 16 04:39:11 MST 2015
Dear all,

I am using FlashMagic to flash an LPC1788 on a custom board.
I have already been able to correctly flash some LPC1763 using same USB to serial cable and same configuration.

With the LPC1788 I almost always get the auto baud error.  I have connected my logic analyser on both RX and TX and found everything correct, the LPC1788 answer with the "Synchronized\r\n" command. I have tried to send from the FashMagic terminal the sync character '?' and get the following answer: "“ùîãèòïîéúåä" instead of the expected "Synchronized\r\n".

Accordingly to my logic analyser the bit rate of the answer is 108108 bits/s instead of the expected 115200.
I have tried to reduce speed to 38400 and the LPC1788 answer at 37735. For 19200 the LPC1788 answer at 19323.

Does anybody have any idea why my LPC1788 answer using the wrong speed when using 115200 ? I have no external quartz and use the internal RC oscillator.

Thanks in advance

[lpcware]

Content originally posted in LPCWare by pgr on Tue Mar 17 06:08:30 MST 2015
@nerd herd
Yes it works at 9600, the issue I had was at 115200 but I have now found why.

@wmues
It's a good idea, I will probably do something similar. I will try to found a chip in revision "F" that seems to fix this issue.

[lpcware]

Content originally posted in LPCWare by wmues on Mon Mar 16 13:57:52 MST 2015
I have written a very small program in internal RAM which is setting the speed of the ISP to 115 KBaud.
This program is loaded via ISP @ 56K, and the following flash code is loaded @ 115K.

In mass production, time is money.

[lpcware]

Content originally posted in LPCWare by nerd herd on Mon Mar 16 08:00:00 MST 2015
Hi pgr,

Have you tried using 9600 as the baud rate for the synchronization character ("?")? Also, what version of flash magic are you using? One other test you can do is to run a simple program that outputs the IRC on the CLKOUT pin to make sure your IRC is running at a solid 12 MHz.

[lpcware]

Content originally posted in LPCWare by pgr on Mon Mar 16 05:59:19 MST 2015
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[lpcware]

Content originally posted in LPCWare by pgr on Mon Mar 16 05:24:47 MST 2015
Just found the following on the ES_LPC177x/8x errata sheet:

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Quote:
3.8 ISP.1
Introduction:
In-System Programming (ISP) is programming or reprogramming the on-chip flash
memory, using the boot loader software and UART0 serial port. This can be done when
the part resides in the end-user board.
Problem:
UART ISP cannot be used at rates higher than 57,600 bits per second.
Work-around:
UART ISP must be used at 57,600 bits per second or a lower communications speed.

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[lpcware]

Content originally posted in LPCWare by pgr on Mon Mar 16 05:20:39 MST 2015
Yes it's 3.3V. What it's really strange is that everything is working fine with LPC1763 but with LPC1788 I got speed error. It's as the LPC1788 have an internal issue to autobaud correctly for 115200...

[lpcware]

Content originally posted in LPCWare by R2D2 on Mon Mar 16 04:50:26 MST 2015

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Quote: pgr
...same USB to serial cable...

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:quest:

3.3V ?