Communication problems with MCB900 (FM3.71)

[jajaen]

hi,

I programmed a 89LPC935 using an MCB900 just a few hours ago, i was using FM3.50 and a USB to RS232 convertor.
the program was running fine but when i tried to reprogram it a couple of minutes later, i could not communicate with the MCB900 board.
I have tried everything suggested in "andy eyre's read first tips" but nothing seames to help, also upgraded to FM3.71 but that doesn't help either.
Even when i tried to connect the board later on by using a real RS232 it didn't help.
any suggestions please?

thanks!

[Andy Ayre]

Go to Options -> Advanced Options and turn on the DTR and RTS option.
Make sure the jumper is in the Run position.

Now does it work?

Andy

[jajaen]

thanks for the tip but...

tried it and it still doesn't work, lowered the baud rate, still doesn't work...

jajaen.

[Andy Ayre]

Sorry, the jumper should be in the Reset position. So to summarise:

Avoid USB cables - DTR and RTS often don't work properly
Jumper in Reset position
DTR and RTS option turned on in Advanced Options in Flash Magic
7200 baud
No interface selected in step 1 of the main window in Flash Magic

Does that help?

Andy

[jajaen]

nope, still doesn't work! we programmed it in the standard confguration for the 89LPC935, is it possible that something went wrong here?
now i've put a 89LPC936 in the MCB900, tried to read the device configuration and it worked, does this mean that the USB to RS232 isn't the problem? so we only have the problem with the previously programmed 935....is it possible that we managed to ruin it?

thanks!

edit : just noticed that we put our oscillator frequency in step 1 on 12MHz,  but when we read out the LPC936 it said 7.367 +- 2.5% is it possible that we programmed the LPC935 on a frequency of 12MHz while it was actually working on 7.367MHz and it stopped working ever since?

[Andy Ayre]

No, the frequency isn't programmed into the device.

The devices arrive from the factory with the status bit set, so on reset they enter ISP mode. Once you program the device Flash Magic clears the status bit so that on the next reset your firmware will execute. Now you have to get the device back into ISP mode by using one of the methods in the datasheet. If you fail to get it into ISP mode it now looks like you just broke the device by programming it.

So, can you program your LPC936, execute the firmware and then program it again? If so then I would suspect the LPC935 is damaged. However if you have the same problem with the LPC936, then I think the problem is getting both devices back into ISP mode again. The next step at that point would be to put a scope on the Reset and VCC pins and verify that the reset pin is receiving three pulses after the device is powered up.

I'm not sure what you mean about "programmed it in the standard configuration". If you went to ISP -> Device Configuration and changed the settings there then the device may now need an external crystal for the oscillator, for example.

Andy