Lpc2000

On Wednesday, July 7, 2004, at 08:30 PM, Robert Adsett wrote:

> At 07:47 PM 7/7/04 -0700, you wrote:
>> It would be nice if Philips provided a reliable (as in supported)
>> mechanism to get back into the bootloader from user code.
>
> Not to pick on you in particular, but this seems an awful lot of angst 
> over
> bringing out one more connection.  If you are going to allow ISP after
> potting you have bring out a minimum of 3 signals anyway (TxD, RxD and
> Gnd), 5 if you provide power and control the reset.  Adding 1 to 
> control
> P0.14 really doesn't seem like a big deal.  Actually the only element 
> that
> comes to mind is if you are reusing a connector with predefined 
> meanings
> and can't reuse an existing pin definition for programming.
>
> In addition, it is possible to get into a situation where the part is
> partially programmed and therefore won't enter ISP mode automatically 
> but
> there isn't a valid user program to force a shift to ISP mode.  If 
> P0.14 is
> not brought out in some fashion then any boards that get stuck here 
> will
> have to be tossed.
>
> I think if you need to be able to program parts reliably w/o using 
> P0.14
> you will need to devote the first sector to a code that is never 
> erased and
> provides a way to program the remaining 14 sectors with the application
> code.  The first sector might also provide other support code (maybe
> diagnostics, a way to initialize the hardware to a good, safe start
> condition etc...
>
>

I would agree! I have no angst on this issue, it just seemed like it 
might be a useful thing which wouldn't be that hard to do from the 
bootloader side. In my particular case I have a separate chip driving 
the programming - I'm using a TUSB3410 to provide a usb->uart interface 
and then driving P0.14 and RST with two of it's GPIO's. So far it works 
well.

The LPC210x parts are pretty tight on GPIO, in that sense a 
non-external bootloader entry would be nice (except that you would 
still have to guarantee logic high on reset), but as you point out it 
would only work if you can get to it reliably (or are willing to accept 
some amount of un-reliablity). If you did devote the first sector 
towards an additional bootloader you could just have it do diags and 
then call the philips bootloader for programming. Still seems like a 
lot of work.

Shannon