Messages

Game,

does your code actually set up port2 to push-pull outputs? I am not convinced that including stdio does this for you, and they may be operating as inputs or open-collector, which would not feed current to your LEDs.

try adding the line:

P2M1 = 0;

before writing to the port


n

Thank you Erik, Jan and Andy

These are excellent suggestions.

I will try switching clock sources on the fly as Erik suggests. I wonder if I would need to account for the very slow start up and stabilisation of the crystal clock? The pulse of power to the RC clock while waiting a second for the crystal to power up would still be a very small expenditure of energy.

Tomorrow I'll program a chip to put out its CPU clock/2 on the designate d pin and use that as an external  clock source to inject into a 'locked  up' chip in the mcb board. I know now that Jan is right about the flash setting not strongly determining the working  frequency becuase when I just touched the pin for the clock input  on a programmed chip it picked up the UK 100 Hz mains hum from my finger and executed the firmware very slowly.

Andy, I had hoped to put off learning how to do ICP but maybe I'll bring that forward, now.


thanks chaps.

n

Thanks to Erik and Andy for advice.

Erik suggested finding baud rates that will work with this slow clock frequency. I had tried r-e-a-l-l-y slow, but had not thought of trying particular baud rates that the system might prefer, so I tried baud rates proportioned to the difference between the RC clock and the crystal. No luck.

Andy, I thinkl I am going to have to develop with faster clocks and dividing down the clock source in the clock divider, but in the end I will have to switch to 32 khz because the power consumption in total power-down with just the real-time clock running is < 1 microamp (my measurement,) which is just what I need.  This final stage of development might therefore cost me a chip every time I want to improve the software!


thanks again.

Nigel

Hello,

am I diagnosing my problem correctly?

I am happily programming and reprogramming p89lpc932's on the MCB900 with Flashmagic while using the chip's RC oscillator.

But when I worked up an application using a low-power 32.778 crystal and set the flash options accordingly, I found I could program the chip once, but not reprogram with later versions of my program.  Flashmagic says it can't connect at the baud rate.

I went through a few chips before I thought:

 Duh!  If each chip is set to use a low frequency clock source, it can't use its own UART properly, so the MCB900 board can't communicate with it on future occasions. I tried reducing the baud rate to 2400, 300 and finally 1 baud! No luck.

Is this really what's happening or is there something I don't understand?

Is there a way round it so as to be able to reprogram chips with 32khz clocks?

I have burned up so many P89LPC 932 I need a new stock.
I got excellent service from Quarndon Elecrtronics once before, but it took them weeks to supply me. Anyone know where I can get a couple of dozen fast?

best.

Nigel