software serial (and support for additional UARTs)

[soundanalogous]

A number of requests have been made to add software serial support to Firmata. I think instead of just software serial, it would be better to support both software serial and additional UARTs (on a Mega for example: Serial1, Serial2, etc).

For those who are asking for serial support in Firmata, what are your use cases?

• read only serial devices?
• read/write serial devices
• board to board communication over serial?
• anything else?

I need to know this in order to determine how much of the Stream interface to expose. In the simplest example I assume a read buffer and a write buffer would be sufficient - simply echoing the serial data. However are there also use cases that would need the peek() or flush() methods. There are also limitations in buffer sizes (64 bytes incoming... but you have to split every byte so you only get 32 bytes... even less actually after stripping out the command bytes so more like 29 or 30 bytes of actual data).

Software serial also interferes with some timer-based features. So PWM may not work as expected when using Software serial. There are other potential collisions as well. However this can be avoided by using a Leonardo, Mega or other board that has separate hardware serial ports (Serial1, Serial2, etc). It would use the same protocol as SW serial with the main difference being that you'd configure with a port number rather than a pair of pin numbers.

[kamituel]

My use case is reading RFID tags using this module. So it falls into "read-only serial devices" category.

AFAIK I need to access following methods on SoftwareSerial (which inherits from Stream):

• begin()
• available()
• read()

#include <SoftwareSerial.h>

SoftwareSerial rfid = SoftwareSerial(5, 6);
rfid.begin(9600);

while(rfid.available() > 0) {
    c=rfid.read();
    // ...
}

(source)

I'm using Adruino Duemilanove.

Thanks for openining this issue, @soundanalogous.

[jtrinklein]

My use case is board to board communication. I am in the read/write category.

[soundanalogous]

Board to board communication via software serial with one of the boards having a hardware serial (or Ethernet or WiFi) connection to a Firmata client application?

[jtrinklein]

Here is my setup: I have a raspberry pi with serial connection to arduino with one way communication pi writes, arduino reads. Then I have the arduino connected to another arduino with another one way communication setup.
Pi [Tx] -> [Rx] arduino1[Tx] -> [Rx] arduino2

[soundanalogous]

So in your setup, arduino1 would be running StandardFirmata. Arduino 2 is
connected to Arduino1 via SoftwareSerial and you have a firmata client
application running on the Pi that communicates with arduino 1 via Firmata
and would be able to communicate with Arduino 2 through Arduino 1 using
SoftwareSerial through Firmata?

On Sun, Nov 3, 2013 at 4:20 PM, James Trinklein notifications@github.comwrote:

Here is my setup: I have a raspberry pi with serial connection to arduino
with one way communication pi writes, arduino reads. Then I have the
arduino connected to another arduino with another one way communication
setup.
Pi [Tx] -> [Rx] arduino1[Tx] -> [Rx] arduino2

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/97#issuecomment-27654679
.

[jtrinklein]

Yep, you got it.

[soundanalogous]

Some initial thoughts on a protocol:

// config: creates new SoftwareSerial instance and calls begin(baud)
0  START_SYSEX  (0xF0)
1  SW_SERIAL    (0x60)  // command byte
2  CONFIG       (0x00)  // subcommand byte
3  txPin        (0-127) // restrictions apply per board
4  rxPin        (0-127) // restrictions apply per board
5  baud         (bits 0 - 6)
6  baud         (bits 7 - 13)
7  baud         (bits 14 - 20)
8  END_SYSEX    (0XF7)

// SoftwareSerial instantiation needs to be deferred
#inclde <SoftwareSerial.h>
SoftwareSerial *mySerial = NULL;

void setup() {}

void loop() {
  if (!mySerial) {
    mySerial = new SoftwareSerial(txPin, rxPin);
    mySerial->begin(baud);
  }
}

// read contents of sw serial buffer and send to Firmata client
0  START_SYSEX  (0xF0)
1  SW_SERIAL    (0x60)
2  SW_SERIAL_TX (0x01)
3  txPin        // used to identify port (may remove this)
4  data 0       (LSB)  // each byte is split
5  data 0       (MSB)
6  data 1       (LSB)
7  data 1       (MSB)
...             // up to max buffer - 5
n  END_SYSEX    (0XF7)

// example implementation
if (mySerial->available() > 0) {
  Firmata.write(START_SYSEX);
  Firmata.write(SW_SERIAL);
  Firmata.write(SW_SERIAL_TX);
  Firmata.write(txPin);
  Encoder7Bit.startBinaryWrite();
  while (mySerial->available() > 0) {
    Encoder7Bit.writeBinary(mySerial->read());
  }
  Encoder7Bit.endBinaryWrite();
  Firmata.write(END_SYSEX);
}

// receive serial data from Firmata client, reassemble and
// call mySerial->write(data) for each byte
0  START_SYSEX  (0xF0)
1  SW_SERIAL    (0x60)
2  SW_SERIAL_RX (0x02)
3  rxPin        // used to identify port (may remove this)
4  data 0       (LSB)
5  data 0       (MSB)
6  data 1       (LSB)
7  data 1       (MSB)
...             // up to max buffer - 5
n  END_SYSEX    (0XF7)

// example implementation
handleSWSerialRX(byte argc, byte *argv)
{
  byte data;
  // argv[0] is subcommand
  // argv[1] is rxPin

  // reassemble data bytes and forward to sw serial write buffer
  for (byte i = 2; i < argc; i += 2) {
    data = argv[i] + (argv[i + 1] << 7);
    mySerial->write(data);
  }
}

// call mySerial->flush()
0  START_SYSEX      (0xF0)
1  SW_SERIAL        (0x60)
2  SW_SERIAL_FLUSH  (0x03)
3  txPin            // used to identify port (may remove this)
4  END_SYSEX        (0XF7)

[maerzhase]

anybody realized the firmata working with softserial? i am working on a project that would profit from it aswell

[soundanalogous]

I need to find some time to work on it.

[ClintonKeith]

I'm using the Romeo DF Robot Controller:
http://www.dfrobot.com/index.php?route=product/product&filter_name=romeo&product_id=844#.Utnpz3mtvqa

Which is based on the Leonardo. It has a built-in XBee socket connected to the hardware serial (Serial1). This is a perfect platform for Johnny-five! Hopefully this fix will happen.

[soundanalogous]

I've taken an initial pass at an implementation (based on the protocol I drafted above). It is available in my fork in the softserial branch. It compiles in Arduino 1.0.5 (we're currently having issues compiling configurable firmata in Arduino 1.5.x). You'll find SoftSerialFirmata in the examples folder. Compile and upload to an Arduino using Arduino IDE version 1.0.5. I haven't created any client examples yet so this is all still theory at this point until proven through a working example.

[soundanalogous]

This is the protocol for the preliminary implementation. It differs from what is above in that for now I'm limiting to only a single SoftwareSerial instance so the rxPin and txPin are not included in the SW_SERIAL_RX and SW_SERIAL_TX commands.

Also this will only work for software serial (wrapping the Arduino SoftwareSerial library). Hardware Serial (Serial1, Serial2, etc) poses another set of challenges.

// config: creates new SoftwareSerial instance and calls begin(baud)
0  START_SYSEX  (0xF0)
1  SW_SERIAL    (0x60)  // command byte
2  CONFIG       (0x00)  // subcommand byte
3  txPin        (0-127) // restrictions apply per board
4  rxPin        (0-127) // restrictions apply per board
5  baud         (bits 0 - 6)
6  baud         (bits 7 - 13)
7  baud         (bits 14 - 20)
8  END_SYSEX    (0XF7)

// read contents of sw serial buffer and send to Firmata client
0  START_SYSEX  (0xF0)
1  SW_SERIAL    (0x60)
2  SW_SERIAL_TX (0x01)
3  data 0       (LSB)  // each byte is split
4  data 0       (MSB)
5  data 1       (LSB)
6  data 1       (MSB)
...             // up to max buffer - 5
n  END_SYSEX    (0XF7)

// receive serial data from Firmata client, reassemble and
// call mySerial->write(data) for each byte
0  START_SYSEX  (0xF0)
1  SW_SERIAL    (0x60)
2  SW_SERIAL_RX (0x02)
3  data 0       (LSB)
4  data 0       (MSB)
5  data 1       (LSB)
6  data 1       (MSB)
...             // up to max buffer - 5
n  END_SYSEX    (0XF7)