Support for USB slave functions on smaller micro's (e.g. LPC11U23)

[pbrier]

When using smaller microcontrollers, like the LPC11U23, some USB functions take up a considerable amount of memory, and do fit or leave too little memory for useful work (depending on compiler and std. libraries used; KEIL performing better than GCC). One solution is not to include the Stream class, and remove this from the USB classes. Now it does fit (of course you loose the standard Stream functionality on the interface):

For example: modify line 92 of USBKeyboard.h from:

class USBKeyboard: public USBHID, public Stream {

to

class USBKeyboard: public USBHID {

Note: A similar issue is occurs with the Serial() class, you can remove the Stream or access the C-api directly to conserve memory.

Question: Can a build option be provided for compilation without Stream classes?
(e.g. NOCPPSTREAM?)

[emilmont]

Hi Peter,
did you collect some numbers about how much memory it would save?

Thanks,
Emilio

[mbednotifications]

On Monday, September 16, 2013 1:13:56 PM UTC-4, Peter Brier wrote:

When using smaller microcontrollers, like the LPC11U23, some USB functions
take up a considerable amount of memory

NXP LPC11Uxx, LPC18xx and LPC43xx MCUs include a USB device stack in ROM
that can reduce code and memory size requirements for implementing USB
devices. It supports CDC, DFU, HID, MSC and custom classes, including
composites. Documentation is somewhat weak, so a solid implementation
usually takes some iteration. We have used it with our LPC43xx boards and
it works well. May consider adding support for it in the mbed LPC43xx port
later this year.

http://docs.lpcware.com/usbromlib/v1.0/

Regards,
Jesus Alvarez

[mbednotifications]

You could also consider to disable DEVICE_STDIO_MESSAGES. Those take up
quite some memory as well.

On Monday, September 16, 2013 10:13:56 AM UTC-7, Peter Brier wrote:

When using smaller microcontrollers, like the LPC11U23, some USB functions
take up a considerable amount of memory, and do fit or leave too little
memory for useful work (depending on compiler and std. libraries used; KEIL
performing better than GCC). One solution is not to include the Stream
class, and remove this from the USB classes. Now it does fit (of course you
loose the standard Stream functionality on the interface):

For example: modify line 92 of USBKeyboard.h from:

class USBKeyboard: public USBHID, public Stream {

to

class USBKeyboard: public USBHID {

Note: A similar issue is occurs with the Serial() class, you can remove
the Stream or access the C-api directly to conserve memory.

Question: Can a build option be provided for compilation without Stream
classes?
(e.g. NOCPPSTREAM?)

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Reply to this email directly or view it on GitHubhttps://github.com//issues/68
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[ciarmcom]

ARM Internal Ref: IOTMORF-330

GitHib issue review: Closed due to inactivity. Please re-file if critical issues found.