Hello,
I have few questions on what I want to do.
<https://lh4.googleusercontent.com/-ez6O-wfZRHM/U3DaTJ1_XzI/AAAAAAAACw8/Io7KgMwfFKA/w890-h503-no/2014-05-12>I
am trying to sent information from and android device to the ioio to an
FPGA board. I am using SPI protocol to send this info to the FPGA. The
information that needs to be sent is stored in a byte array in the phone
which is split in smaller arrays (64 bytes are max bytes that can be sent
in one package(?)) and sent to the ioio. For now I choose a speed of 8MHz.
I for now created a signal with alternating bits. From reading the
resulting output (on the MOSI pin) with an oscilloscope I get a signal as
seen in the picture to the right. This shows me that 8 bytes per approx. 3
microseconds are sent with each containing 8 bits(which is correct).
-
*Is everything I assumed/explained/observed so far correct?(e.g. the max
package size) *
-
*is it possible to invert the MOSI or SS from the Android app code? *
- *Is there a way to decrease the 3 microseconds per 8bytes?*
Altogether what would be more advantageous to us is to have a constant flow
of bits being sent at >1MHz(so no stop in between from initialization of
the stream. say if I send 16 bits, I do not want there to be a small space
of nothing between 2 bytes(8bits)). If above is true then SPI won't be able
to achieve this.
- *Any advice on how to achieve this? Or is it just better to continue
with SPI?*
I made a post before about what I am ultimately trying. I want to send a
picture with the android to the IOIO and make the IOIO sent it on to an
FPGA board which will drive a custom LED matrix system. The android will
send bytes with R,G and B values in that order for each pixel and that info
will be further handled at the FPGA.
The code for sending the bytes through the IOIO is as follows:
> @Override
> public void loop() throws ConnectionLostException {
>
> byte[] buffer_= buffer;
> int buffernum = (int) Math.ceil(buffer_.length/8);
>
> byte[] buffer1_= new byte[64];
> byte[] buffer2_= new byte[64];
> for (int i =0;i<buffernum;i++){
> System.arraycopy(buffer_, i*64, buffer1_, 0, 64);
> if ((i+1)<buffernum){
> System.arraycopy(buffer_, ++i*64, buffer2_, 0, 64);
> }
> try {
> ioio_.beginBatch();
> Thread.sleep(1);
>
> if ((i+1)<buffernum){
> spi_.writeReadAsync(0,buffer2_, buffer2_.length,
> buffer2_.length, null, 0);
> }
> spi_.writeRead(buffer1_, buffer1_.length,
> buffer1_.length, null, 0);
> ioio_.endBatch();
> } catch (InterruptedException e) {
> // TODO Auto-generated catch block
> e.printStackTrace();
> }
> }
>
> }
>
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