programming an arduino to read sd card and send lines of text over serial

[Geekinesis]

Hi
I know its possible to tell an arduino to read a file from an SD card.
I would like to parse a file and send one line at a time over a serial
link. Waiting for a serial text reply before sending the next line.

The idea is to send gcode to a second arduino running grbl. So far I
am sending the code with a PC.

Is this relatively straightforward to do? I have little arduino
experience.

I am working on a cnc plotter project which I want to enter into
Brighton make fair.

[Tim Hutt]

On 22 June 2011 15:27, Geekinesis <geeki...@googlemail.com> wrote:
> Hi
> I know its possible to tell an arduino to read a file from an SD card.
> I would like to parse a file and send one line at a time over a serial
> link. Waiting for a serial text reply before sending the next line.
>
> The idea is to send gcode to a second arduino running grbl. So far I
> am sending the code with a PC.
>
> Is this relatively straightforward to do? I have little arduino
> experience.

I've never done SD card stuff, but serial is very simple:
http://arduino.cc/en/Tutorial/ASCIITable

By the way, the easiest way I've found to do serial comms from a
computer is using boost's asio serial library. I have some example
code if anyone wants...

[Nicholas FitzRoy-Dale]

On 22/06/2011, at 3:27 PM, Geekinesis wrote:

> Hi
> I know its possible to tell an arduino to read a file from an SD card.
> I would like to parse a file and send one line at a time over a serial
> link. Waiting for a serial text reply before sending the next line.
>
> The idea is to send gcode to a second arduino running grbl. So far I
> am sending the code with a PC.
>
> Is this relatively straightforward to do? I have little arduino
> experience.

The hardware portion is pretty trivial, as is the code required to read raw data from the SD card, since SD cards support SPI:

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1235125412/all

If you have an actual file system on there, you will have to also implement a FAT filesystem reader (some are linked in the thread). You might find it easier just to write the gcode to the SD card in raw format (i.e. using dd on Unix) and avoid the filesystem altogether.

Nicholas

[tom]

I'll be trying this at some point soon as I want to build a datalogger
for a mad idea i have, if i get anywhere i'll post and let you know :)

On Jun 22, 4:25 pm, Nicholas FitzRoy-Dale

[Daniel Sikar]

Wiring up TXD, RXD, RTS# and CTS# between Arduinos should be
straightforward.

[Martin Klang]

TX to RX and RX to TX is all you need for two-way comms. I wouldn't worry about hardware flow control.

Any reason you can't get the second arduino to read from the SD card itself?

/m

[Geekinesis]

hi
Its more the code for parsing of the text file and sending line by
line I am trying to work out.

[Mark Steward]

This is as simple as (after installing python-serial):

import serial

# Set this to the right one for your system:

dev = '/dev/ttyUSB0'

#dev = '/dev/ttyACM0'

#dev = '/dev/tty.usbserial123456'

arduino = serial.Serial(dev, 115200)

with open('file.txt') as file:

  for line in file:

    arduino.write(line)

    input = arduino.readLine()

Mark

[Daniel Sikar]

Here's a suggestion sending byte by byte - grbl can deal with carriage
returns:

file myfile;
byte outbyte;

int sendgcode2grbl(string filename)
{
// initialise sd card and open file
SD.begin();
if(!(SD.exists(filename)))
return 0;
myfile = SD.open(filename, FILE_READ);

// initialise serial port
Serial.begin(9600);

// send data one byte at a time
outbyte = myfile.read();
while(outbyte>-1)
{
Serial.write(outbyte);
outbyte = myfile.read();
}

// tidy-up
Serial.end()
myfile.close();
return 1;

[Mark Steward]

Ahh, I misread the original request.  What an idiot.

[Geekinesis]

ah but you read my mind, I was looking for a python solution as well
that I could run from linux.

Thanks for the code daniel, I will experiment.