Name:
=====
 ios_fifo


Description:
============
 Example slave used for demonstrating the use of the IOS FIFO.


Purpose:
========
This slave component runs on one EVB and is used in conjunction with
the companion host example, ios_fifo_host, which runs on a second EVB.

The ios_fifo example has no print output.
The host example does use the ITM SWO to let the user know progress and
status of the demonstration.

This example implements the slave part of a protocol for data exchange with
an Apollo IO Master (IOM).  The host sends one byte commands on SPI/I2C by
writing to offset 0x80.

The command is issued by the host to Start/Stop Data accumulation, and also
to acknowledge read-complete of a block of data.

On the IOS side, once it is asked to start accumulating data (using START
command), two CTimer based events emulate sensors sending data to IOS.
When IOS has some data for host, it implements a state machine,
synchronizing with the host.

The IOS interrupts the host to indicate data availability. The host then
reads the available data (as indicated by FIFOCTR) by READing using IOS FIFO
(at address 0x7F).  The IOS keeps accumulating any new data coming in the
background.

Host sends an acknowledgment to IOS once it has finished reading a block
of data initiated by IOS (partially or complete). IOS interrupts the host
again if and when it has more data for the host to read, and the cycle
repeats - till host indicates that it is no longer interested in receiving
data by sending STOP command.

Printing takes place over the ITM at 1M Baud.

Additional Information:
=======================
In order to run this example, a host device (e.g. a second EVB) must be set
up to run the host example, ios_fifo_host.  The two boards can be connected
using fly leads between the two boards as follows.

Pin connections for the I/O Master board to the I/O Slave board.
SPI:
HOST (ios_fifo_host)                    SLAVE (ios_fifo)
--------------------                    ----------------
GPIO[10] GPIO Interrupt (slave to host) GPIO[4]  GPIO interrupt
GPIO[5]  IOM0 SPI SCK                   GPIO[0]  IOS SPI SCK
GPIO[7]  IOM0 SPI MOSI                  GPIO[1]  IOS SPI MOSI
GPIO[6]  IOM0 SPI MISO                  GPIO[2]  IOS SPI MISO
GPIO[11] IOM0 SPI nCE                   GPIO[3]  IOS SPI nCE
GND                                     GND

I2C:
HOST (ios_fifo_host)                    SLAVE (ios_fifo)
--------------------                    ----------------
GPIO[10] GPIO Interrupt (slave to host) GPIO[4]  GPIO interrupt
GPIO[5]  IOM0 I2C SCL                   GPIO[0]  IOS I2C SCL
GPIO[6]  IOM0 I2C SDA                   GPIO[1]  IOS I2C SDA
GND                                     GND


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