user8570: Objective: interface and Arduino MEGA to a Mettler Toledo SB32001 using the RS-232 communication protocol described in the manual. 
Equipment Used:

SB32001 Mettler Toledo 32 kg scale
Arduino MEGA
Sparkfun RS232 Shifter - SMD

Background:
I am using the SoftwareSerial library to try to communicate with the scale through MEGA pins 52 and 53. I have the level shifter connected to the scale using a through cable. 
So far, I have tried to send the most basic command to the scale, and the command is both not executing, and not causing a status code to be send back (i.e. failure OR success). My Tx light on the level shifter flashes, but the Rx light never does.
Write string to screen:
D "String"
Because I have a through cable, I have tried switching the Tx and Rx pins in code. Neither has worked.
The from the scale has the following options I can set:

Baud Rate: 150, 300, 600, 1200, 2400, 4800, 9600
Parity: 7b-E, 7b-no, 8b-no, 7b-odd

Here is a minimal (non)working example of my code:
#include <SoftwareSerial.h>

const int pinTX = 53;
const int pinRX = 52;

scale = SoftwareSerial(53, 52);

void setup(){
    Serial.begin(9600);
    scale.begin(9600);
    delay(100);
}

void loop(){
    scale.println("D \"Hello!?\"");
    delay(100);

    while (scale.available()){
        Serial.print(scale.read());
    }
    Serial.println()
    delay(100);
}

What I need:
I need help figuring out where I should look next to solve this issue. I have tried switching the transmit and receive pins in software. I have tried using jumpers to switch the Tx and Rx pins in hardware. I have tried 7 and 8-bit settings with no parity. Nothing give me a signal back. Totally perplexed?
Is it my converter chip? Does anyone know of problems with this shifter? I know that it does not contain the industry standard MAX232

user8570: The solution turned out to be a couple of things, some of which mentioned by others in the comments.
Problems that needed to be fixed:

My level-shifter was a huge part of the problem. I switched to a MAX232-based chip and then I was a least able to get responses shorted lines 2 and 3 (Tx and Rx).
I needed a cross-over cable. I had tried this while troubleshooting, but because that alone didn't fix the problem, I had not idea whether or not that was the problem, or just one of the problems.
I needed to use the onboard UART (Serial1) rather than SoftwareSerial. The problem was that I needed to be able to set the protocol to 8 bits with no parity. This configuration parameter cannot be changed on SoftwareSerial, but is as simple as Serial1.begin(9600, SERIAL_8N2).

Thank you for the help, and hopefully my mistakes make the process easier for others.

8570: <p><strong>Objective:</strong> interface and Arduino MEGA to a Mettler Toledo SB32001 using the RS-232 communication protocol described in <a href="https://us.mt.com/mt_ext_files/Editorial/Generic/7/MT-SICS_for_Excellence_Balances_BA_Editorial-Generic_1116311007471_files/Excellence-SICS-BA-e-11780711B.pdf%22the%20manual%22" rel="nofollow">the manual</a>. </p>

<p><strong>Equipment Used:</strong></p>

<ul>
<li>SB32001 Mettler Toledo 32 kg scale</li>
<li>Arduino MEGA</li>
<li><a href="https://www.sparkfun.com/products/449" rel="nofollow">Sparkfun RS232 Shifter - SMD</a></li>
</ul>

<p><strong>Background:</strong></p>

<p>I am using the <code>SoftwareSerial</code> library to try to communicate with the scale through MEGA pins 52 and 53. I have the level shifter connected to the scale using a through cable. </p>

<p>So far, I have tried to send the most basic command to the scale, and the command is both not executing, and not causing a status code to be send back (i.e. failure OR success). My Tx light on the level shifter flashes, but the Rx light never does.</p>

<p>Write string to screen:</p>

<p><code>D "String"</code></p>

<p>Because I have a through cable, I have tried switching the Tx and Rx pins in code. Neither has worked.</p>

<p>The from the scale has the following options I can set:</p>

<ul>
<li><strong>Baud Rate:</strong> 150, 300, 600, 1200, 2400, 4800, <strong>9600</strong></li>
<li><strong>Parity:</strong> 7b-E, 7b-no, <strong>8b-no</strong>, 7b-odd</li>
</ul>

<p>Here is a minimal (non)working example of my code:</p>

<pre><code>#include &lt;SoftwareSerial.h&gt;

const int pinTX = 53;
const int pinRX = 52;

scale = SoftwareSerial(53, 52);

void setup(){
    Serial.begin(9600);
    scale.begin(9600);
    delay(100);
}

void loop(){
    scale.println("D \"Hello!?\"");
    delay(100);

    while (scale.available()){
        Serial.print(scale.read());
    }
    Serial.println()
    delay(100);
}
</code></pre>

<p><strong>What I need:</strong></p>

<p>I need help figuring out where I should look next to solve this issue. I have tried switching the transmit and receive pins in software. I have tried using jumpers to switch the Tx and Rx pins in hardware. I have tried 7 and 8-bit settings with no parity. Nothing give me a signal back. Totally perplexed?</p>

<p>Is it my converter chip? Does anyone know of problems with this shifter? I know that it does not contain the industry standard MAX232</p>
 8570: <p>The solution turned out to be a couple of things, some of which mentioned by others in the comments.</p>

<p>Problems that needed to be fixed:</p>

<ol>
<li><p>My level-shifter was a huge part of the problem. I switched to a MAX232-based chip and then I was a least able to get responses shorted lines 2 and 3 (Tx and Rx).</p></li>
<li><p>I needed a cross-over cable. I had tried this while troubleshooting, but because that alone didn't fix the problem, I had not idea whether or not that was the problem, or just one of the problems.</p></li>
<li><p>I needed to use the onboard UART (Serial1) rather than SoftwareSerial. The problem was that I needed to be able to set the protocol to 8 bits with no parity. This configuration parameter cannot be changed on SoftwareSerial, but is as simple as <code>Serial1.begin(9600, SERIAL_8N2)</code>.</p></li>
</ol>

<p>Thank you for the help, and hopefully my mistakes make the process easier for others.</p>
