(r4) ImplementingTheArduinoToolbox < Embedded

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---+ Implementing the Arduino toolbox
---++ The program structure

As you would probably expect, the program will consist of three parts
   * a server running on the Arduino taking commands from Xcos and accessing the GPIO hardware
   * an Xcos client implementing the Xcos blocks
   * a protocol defining the communication between client and server
There is already an Xcos system reading out several sensors and controlling several actuators, mainly motors. Unfortunately this Scilab toolbox works on Windows exclusively. It is however a good starting point for our Linux version. Using the same communication protocol and only changing the OS dependent calls to the serial driver will make both toolboxes largely compatible with each other.

I decided however to re-implement the Arduino server including better debugging features.
---++ The communication protocol

The communication protocol must be as simple and short as possible in order to increase the speed and therefore the maximum possible sampling rate.The server itself is an Arduino sketch consisting essentially of a big switch statement. The first specifies the type of action to be taken or the device to talk to. For the moment only 2 devices are implemented:
   * version: returns the version number of the protocol server on the Arduino
   * digital read or write<br />This allows to read the state of a GPIO line defined in the xcos block or to write a high or low state to this GPIO line. Before the xcos simuation (the scilab program on the PC) is started (pre-simulation) the mode of the GPIO line is set.
   * stepping motor<br />Here we set the GPIO pins associated to the stepping motor pulse to output in the pre-simulation step. The a "do one step" command is sent to the server.
Here is the basic protocol description:
---+++ Getting the server version

*V*: gets the server version code. The server answers with Vab where a is the major and b the minor version number e.g. V13 for version 1.3
---+++ Reading or writing a digital GPIO line

*Dan0* or *Dan1*: attaches GPIO line n. The last character defines if the line is input (0) or output (1). n is the GPIO pin number which can be '1' (0x31) up to '9' (0x39). For higher pin numbers just take the next ASCII characters. Having a look at the ASCII table tells us the pin number 10 will correspond to the ASCII characters with code (0x3A) which is ':', 11 corresponds to ';' and so on.<br /><b>Drn</b>: Read the state of GPIO line n<br /><b>Dwn0</b> or <b>Dwn1 </b>sets the GPIO line n to 0 or 1 respectively.

<img alt="ascii.png" height="294" src="%ATTACHURL%/ascii.png" title="ascii.png" width="637" />
---++ Controlling a stepper motor

In case of the stepper motor we need a means to define which GPIO pin is connected to which stepper motor coil. This is done with a command:

*Sanp*: Where "S" identifies for the stepper motor device, "a" stands for "attach" n is the GPIO pin and p is the pulse (N1 .. N4 or the stepping motor driver module) . The command also programs the GPIO pins as output. Sa21 will therefore attach GPIO pin 2 to the first stepping motor driver input (N1 on the driver card).

*Sm*: moves the stepping motor by 1 step

*Sc*: Clears all coil signals to low
---++ The Arduino server program and the test procedure

With this information it is possible to develop the first version of the Arduino server. Since all it needs is input from the serial line we can write a simple C program to test the server. A program asking for the server version (and printing it) as well as the Arduino server are attached to this TWiki page.

The Arduino server uses debugging code which prints each character received as well as the interpretation in makes out of it to a Softserial port with Rx connected to GPIO pin 11 and Tx connected to pin 10. This Softserial port can be attached to a USB to serial adapter and the output observed with a serial emulator program like minicom. The communication between Scilab and the Arduino happens on /dev/ttyUSB0, the debugging port should therefore be connected to /dev/ttyUSB1 (minicom -D /dev/ttyUSB1).

Both, the test programs as well as the xcos toolbox, pass through the same serial library with the following calls:

<img alt="serialLib.png" height="80" src="%ATTACHURL%/serialLib.png" title="serialLib.png" width="650" />

Since the test programs and the xcos toolbox use the same communication code we can be sure that once the server is tested with the test programs it will also work on the toolbox.

Here is a screen dump of the server output when we first read the server version and then blink the builtin LED (on GPIO pin 13) 5 times:

<img alt="blink2.png" height="532" src="%ATTACHURL%/blink2.png" title="blink2.png" width="702" />

And this is the output from the Arduino server onto /dev/ttyUSB1 when running the stepper motor test:

<img alt="stepper.png" height="228" src="%ATTACHURL%/stepper.png" title="stepper.png" width="254" />

And in fact you see the motor turn when it receives the Sm commands.
---++ How to bring the demo system up

A tar archive with a Xcos toolbox containing Digital Write as well as as a basic stepper motor xcos block is attached to this page:

%ATTACHURL%/arduino-linux_1.5-src.tar.gz

This is the original [[https://atoms.scilab.org/toolboxes/arduino/1.5/][arduino_1.5-src]] archive downloaded from git which I modified to run on Linux. Only _Digital Write_ and the <i>stepper motor module </i>are working. The other modules are still part of the archive but will most probably not work. In the original archive the stepper motor block was removed from the Arduino palettes. It has been put back. The original Arduino sketches have been moved into arduino.old and a new server sketch developed which you find in the arduino folder.

To install everything please
   * create a folder /opt/ucc/scilab
   * unpack the above tar archive into this folder.
Have a look in the arduino folder where you should find the server sketch called toolbox_arduino_v0.2.ino. This sketch must be uploaded onto an Arduino. I used an Arduino Nano but an Uno or Mega should work as well. For debugging I use a Softserial port. Connect your PC via a USB to serial converter to the Arduino. GPIO pin 10 on the Arduino corresponds to the Arduino Tx line (Rx of the USB to serial adapter) and pin 11 corresponds to Arduino Rx (see also the definitions in the sketch).

In arduino/serverTest you will find test programs for the server sketch as well as interface functions in serialLib which interface the XCos block Scilab code to the serial driver. The test program,running on the PC, (have a look at blink2.c) passes through these functions and calls the driver in exactly the same way that Scilab will use. For the moment only 2 such test programs are available:
   * blink2.c reading out the server version and blinking the Arduino builtin LED on GPIO pin 13
   * stepper.c which make the stepper motor move. The coil pins on the stepping motor controller (N1 .. N4) must be connected to Arduino GPIO pins 2..5
Try to make the Arduino server sketch work with these programs first.

Then start Scilab. Load the macros
   * builder.sce
   * loader.sce
   * unloader.sce
Execute the builder.sce script.

You should see something similar to this:

<img alt="builder.png" src="%ATTACHURL%/builder.png" title="builder.png" />

If the builder exits successfully then you can start the loader adding the Arduino features into the Scilab system. This is what you should see:

<img alt="loader.png" height="189" src="%ATTACHURL%/loader.png" title="loader.png" width="543" />

Now you can start xcos either by typing <i>xcos </i>in the command window orr by clicking the Xcos icon (the one looking a bit like an oscilloscope). In the palettes box coming up you should see an Arduino entry:

<img alt="palette.png" height="350" src="%ATTACHURL%/palette.png" title="palette.png" width="527" />

Now you can create a diagram using your new Arduino blocks and run it. The LED should blink or the stepper motor move.

-- %USERSIG{UliRaich - 2019-01-07}%

---++ Comments

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Topic attachments
I	Attachment	History	Action	Size	Date	Who
gz	arduino-linux_1.5-src.tar.gz	r1	manage	1798.6 K	2019-01-16 - 13:28	UliRaich
png	ascii.png	r1	manage	70.1 K	2019-01-07 - 16:49	UliRaich
png	blink.png	r1	manage	38.5 K	2019-01-07 - 16:49	UliRaich
png	blink2.png	r1	manage	61.8 K	2019-01-15 - 14:40	UliRaich
png	builder.png	r1	manage	155.3 K	2019-01-16 - 13:37	UliRaich
png	loader.png	r1	manage	11.2 K	2019-01-16 - 13:37	UliRaich
png	palette.png	r1	manage	29.4 K	2019-01-16 - 13:37	UliRaich
png	serialLib.png	r1	manage	22.5 K	2019-01-15 - 14:28	UliRaich
png	stepper.png	r1	manage	15.1 K	2019-01-15 - 14:28	UliRaich
Topic revision: r4 - 2019-01-16 - UliRaich