LPC932 ISP with watchdog oscillator

[S.Panichi]

Hello,

    I discovered that when I reprogram the UCFG1 in order to use the watchdog oscillator as clock source, after the reset the device doesn't  respond to Flash Magic.
Note: I only reprogrammed the UCFG1. I don't download the application in the flash, hence the status bit is still to 1.
   I think that whatever I change the clock source, the ISP code isn't able to correctly recognize the serial baud rate.

   How can I use the ISP and the watchdog oscillator together ?

[Andy Ayre]

Have you tried the slowest baud rate Flash Magic supports?

Why do you want to use the watchdog oscillator as the clock source rather than using the on-chip oscillator and DIVM, with it's lower tolerence?

[S.Panichi]

Hi Andy,

    I want to use the watchdog oscillator because I need an extremely low power consumption in order to maximize battery life. The power consumption of RC oscillator is approximately 300uA. Instead, the watchdog oscillator consumes only 50uA.

Regards

[S.Panichi]

Good news:

The slowest baud rate Flash Magic supports is 2400 baud.  I try at this speed but it doesn't work.
I try (with Hyperterminal) to trigger the ISP at 1200 and 300 baud. It seem to work at these speeds.
In fact, if we compare the speeds with the clock sources we obtain that 9600 baud@7.373Mhz correspond to about 520 baud@400Khz. All of that if we suppose that DIVM is set to 0 or 1 (no clock division).

Regards

[Andy Ayre]

Hmmm...ok. I'll add in 1200 baud and 300 baud in the next release.

[Andy Ayre]

Sorry, 1200 baud and 300 baud didn't make it into the new version, however you can just type in the baudrate that you want into the baudrate box in section 1. So for example, enter "1200" to use 1200 baud.

[Santhi]

Does programming DIVM with non zero value cause problems with the baud rate generator of LPC932?
We have seen that once DIVM is modified the device doesn"t get connected at the baud rate as per the given calculation. We have to enter ISP and sometimes looking at the acknowledge from the device on a scope if you set the baud rate to a close value ISP programming through Flash Magic works. But every time you cycle power the baud rate seems to change. Has anyone faced similar problem? Any suggestions?
Regards

Santhi

[Suchit]

Hi,

If I try to connect to a new unprogrammed  LPC932, Flash Magic connects. But next time, Flash Magic says "it is unable to connect to the device. Try using lower baud rate."
I tried using lower baud rates even used 400 baud rate by typing manually. But it doesn't work.

Why so??

Regards,
Suchit

[Andy Ayre]

Devices come from the factory with the status bit set, so that on power up they enter ISP mode. After programming, Flash Magic sets the status bit to zero, so that on the next reset your code is executed. The next time you want to enter ISP mode, you are now testing for the first time placing the device into ISP mode.

So are you using the MCB900 board? If not check your schematic diagram matches the MCB900 (link to the schematic is on the Flash Magic web page in the pink block).