3wire v 5wire Serial


3wire v 5wire Serial Last Updated Sunday, October 10, 2010 10:22:50 AM Printer Friendly Version Email A Friend Enter e-mail address of recipient: (Use a comma to separate multiple e-mail addresses.) Enter your e-mail address: Message to attach: We use this address only to tell the recipient who sent the message. We do not save or re-use it in any way. Send Email Cancel By: Richard Blackwell Why use 5 wire instead of 3 wire for Serial Communications. DISCUSSION: Each week we are responsible for communicating with 15-20 new serial devices, and every week we are asked about what cable should be used (3 or 5 wire). Generally speaking everyone understands pulling serial instead of IR to the device gives you two-way communications to the device, but why pull 5 wire with the additional cable cost and termination time? ANSWER: Essentially there are three levels of device communications out there: Some devices say very little over time and what they say is very short (i.e. AV Switcher). Some devices are more chatty, and speak even when not spoken too, but are still pretty brief in conversation (i.e. video projector). Digital Signal Processors (DSP) speak often and when they speak they have a lot to say over a period of time (i.e. ramping levels). This is because audio can be mission critical and sometimes even have legal implications. Imagine if a legal firm pressed the Mute button while in critical mediation, but the message was lost due to traffic collisions and sensitive information was divulged? Ok you say, just up the baud rate. While that might have a positive effect, in the short term (or as a Band-Aid effect) let's discuss why we would use 5-wire cable as a better option. Imagine a one lane tunnel under the Hudson river into New Jersey and there were no traffic lights telling you when to go. What would stop a collision? Ok, so use a 5 wire cable (with hand shaking enabled) and its like adding traffic lights to the tunnel scenario above. If you want to ensure that legal firm gets its mic mute then you need to use 5 wire cables with handshaking enabled. As a general rule of thumb: if a piece of equipment sends more than 200 characters at a time you should consider a 5-wire cable. (Note: My first response is always to use Ethernet and stop using Serial, but the day for 100% Ethernet connectivity is not here.) Rate this: Recent Comments There are currently no comments. Be the first to make a comment. Add a Comment Please add your comment by filling out the field(s) below. First Name Last Initial Email Address Submit Comment Cancel
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3wire v 5wire Serial

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