[Microbit-Python] Maximum Size of Microbit Python Program?‏

Wed Jun 8 04:59:36 EDT 2016

Hi Folks,

Essentially, what David W. said about how it works. It won't make a
difference which environment you use to generate the hex, they work in
the same way.

Let me be very clear: there are two issues relating to "size".

1) The size of the script.
2) The amount of memory used when running the script.

I hope we're all agreed that we're talking about 1 in this instance. Put
simply, it's the size of the Python file that's important here. Think of
it as a measure of the number of characters. Less characters is good.

There is actually a way to get more space for Python files but that
depends upon the file system work we're currently close to landing /
documenting / tooling.

I'll provide more details when things become available.

Best wishes,

N.

On 08/06/16 02:05, Mark Schafer wrote:
> I ran into this problem early on where lots of comments making my code
> too large.
> I could not come up with a solution except some sort of mode in mu (or
> similar IDE) that stripped comments before sending. If you read the
> results back though - you have lost info.  So needs to be tightly
> coupled with IDE :(
> 
> Its an interesting problem because teaching people implies more comments
> but this limits the runnable size to smaller programs. I had to remove
> all of my embedded explanations.
> 
> 
> On 6/8/2016 7:32 AM, Nevil Hunt wrote:
>> Thanks David,
>>  
>> I now see how it is done, so, yes, the comments will use up precious
>> memory space.
>>  
>> FYI I've just tried downloading the latest stand-alone mu editor to
>> see if that allows me to write bigger programs but it doesn't. When a
>> program gets over the same size and I hit "download" nothing happens
>> (i.e. the yellow led doesn't start to flash) but if I delete a few
>> lines of comments, the download  then works.
>>  
>> It sounds like you have already lodged the issue that exceeding the
>> program size limit whether from the web interface or from the mu
>> editor is silent - thanks.
>> It then leaves the other issue as to whether anything can be done to
>> increase the size of program that can be run. My program is really of
>> very modest size.
>>  
>> Anyone else got any thoughts on the matter?
>>  
>>  
>> Nevil
>>  
>> ------------------------------------------------------------------------
>> From: david at thinkingbinaries.com
>> Date: Tue, 7 Jun 2016 19:19:39 +0100
>> To: microbit at python.org
>> Subject: Re: [Microbit-Python] Maximum Size of Microbit Python Program?â€
>>
>> Hi Neville,
>>
>> I'm pretty sure the comments are included - the way it has always
>> worked is that the web interface just appends a small binary header
>> and then your python script to the embedded hex file it has cached in
>> the browser. That way, no processing of the script is required. i.e.
>> hex = [MICROPYTHONHEX + hex(BINARYHEADER) +
>> hex(SCRIPT_INCLUDING_COMMENTS)]
>>
>> Here is a Python version of the code that does that process:
>> https://github.com/bbcmicrobit/micropython/blob/master/tools/makecombinedhex.py
>>
>>
>> I believe that all that Nicholas does in the web interface is the
>> same, but in javascript, as it is easy.
>>
>> That way, of course, just like all of the other editors, it is
>> possible to completely recreate the source from a .hex file (as kids
>> have a habit of not saving the source programs, or not keeping good
>> records as to which source program generated which hex program).
>>
>> So yes, comments take up space.
>>
>> There is a pending question on the area51 proposed stackexchange site
>> at the moment, where I ask how users can know in advance of flashing
>> their micro:bit, whether the program will fit or not. There seems to
>> be no obvious way in any of the editors of getting a read-out of how
>> much of the available memory is used *before* you flash it and find it
>> doesn't fit.
>>
>>
>> The other thing to find out is whether you are running out of flash
>> memory, or running out of runtime memory. I would imagine that
>> Damien's micropython parser ignores comments as it iterates through
>> the flash version of the script file to parse it into bytecode in RAM
>> - but you should check with Damien for clarification of how to work
>> out if this is 'running out of flash' or 'running out of memory while
>> parsing', as I can't find the code for that at the moment
>>
>> Damien?
>>
>>
>>
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