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ytai / ioio

Software, firmware and hardware of the IOIO - I/O for Android
Apache License 2.0
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spiMaster.writeRead write buffer transaction limit #382

Closed chrisws closed 3 weeks ago

chrisws commented 3 weeks ago

Is it possible to increase the SpiMaster transaction limit from 64 to 255 (as per twi/i2c) ?

In firmware/app_layer_v1/spi.c the TX/RX buffers are 255 - so is the limitation just in IOIOProtocol.spiMasterRequest ?

This is to improve the refresh rate of an LCD where the read buffer is length 0.

hannesa2 commented 3 weeks ago

Please make a pull request

chrisws commented 3 weeks ago

Actually - I see now why there is a limit - with this:

writeByte((dataNeqTotal ? 0x80 : 0x00) | (resNeqTotal ? 0x40 : 0x00) | totalBytes - 1);

bit 7 + 8 are status bits, so there is only room for 6 bits to hold the length (63 max)

This corresponds to the SPI_DATA_ARGS definition in firmware/app_layer_v1/protocol_defs.h

So, it would require a firmware change to resolve. For an 128x128 16 bit color LCD the buffer size needs to be a lot larger. I was hoping there was a cheap, java side only fix to improve this. Oh well.

hannesa2 commented 3 weeks ago

So, it would require a firmware change to resolve.

I've no idea how to do this. But when you know more, we could do this, if we have the source of it

chrisws commented 3 weeks ago

The source code for the firmware is in the repository, but I have no idea either.

Hopefully the original author(s) could help with some expert advice.

hannesa2 commented 3 weeks ago

@ytai Maybe you know this ?

hannesa2 commented 3 weeks ago

This is the current state https://github.com/ytai/ioio/pull/191#issuecomment-2154259758