RCU Review: FMA Direct FS 5

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    Contributed by: Greg Covey | Published: February 2004 | Views: 24174 | email icon Email this Article | PDFpdf icon
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    Article by: Greg Covey

    FMA's Flight System 5 Receiver

    The FS5, 5-channel Flight System receiver package represents the leading edge in safe, reliable radio controlled equipment. Equipped with new DSR technology and free Viewer Software, the FS5 receiver protects your aircraft during every phase of the flight!

    Combining unprecedented interference rejection, digital servo support, failsafe operation, radio data readout and other groundbreaking features in a small package, the affordable five channel FS5 works with the FM PPM transmitter you already have (or your PCM transmitter set to PPM mode).

    Full Range, Full Performance
    Universal PPM Operation on positive or negative shifts
    Pre-flight Interference Detection
    Digital Signal Recognition (DSR) for exceptional interference rejection
    Programmable Servo Failsafes
    Flight Stabilization during unclean signal periods
    System Data Output to on-board LED or Viewer PC Software
    Weighs just 0.4 oz. Dimensions: 1.67x0.8x0.58 in. (same as Extreme 5)

    Exclusive Digital Signature Recognition (DSR) technology continuously guards against on-channel interference. In the event of signal loss or overwhelming interference, the FS5 instantly moves servos to their pre-set failsafe positions that are programmed using your transmitter and External Switch/LED (or Viewer Software).

    Before you take-off, the FS5 scans the airways and detects if someone else is on your frequency before you even turn on your transmitter. If there are interfering signals, the FS5 warns you with a bright LED light. This multi-function LED will also check battery voltage and inform you if signal loss was experienced during flight.

    While you fly, exclusive DSR technology continuously guards against interference. You just turn the receiver on and the DSR is automatic. It analyzes the data stream and automatically checks for:

    positive or negative shift
    valid number of pulses (and stores this)
    valid frame length
    valid pulse widths

    After you land, the FS5 tells you how your radio system performed during flight. Each FS5 receiver includes free Viewer Software for extended, graphical data readout. While the Viewer Software isn't required for setting up the FS5, it is a great tool for radio system troubleshooting!

    FS5 System Components:

    The FS5I package includes the External Switch/LED and PC Interface Module with the receiver
    The FS5 package contents can vary from just the receiver to including a (CPD4) Co-Pilot, (FSRES1) External Switch/LED, and FS Receiver Viewer Software with (FSIM1) PC Interfacing module/cable. My review is on the FS5I package that contains everything but the Co-Pilot.

    Package Options:
    FS5I - FS5 Receiver with FS Receiver Viewer Software, FS Receiver External Switch/LED, and FS PC Interface Module
    FS5A - FS5 Receiver with FS Receiver Viewer Software, Co Pilot (CPD4)
    FS5C - FS5 Receiver with FS Receiver Viewer Software, Co Pilot (CPD4), FS Receiver External Switch/LED, and FS P.C. Interface Module

    The FS5 runs an interference check and warns you with a bright LED if someone is transmitting on your channel or if it detects signals — from any source, on any frequency — that might endanger your airplane. This multi-function LED will also check battery voltage and inform you if signal loss was experienced during flight.

    After you land, press the button to get interference and signal loss reports (optional External Switch/LED Module lets you interact with the receiver from outside the aircraft).
    The optional Switch/LED board allows external receiver status and control from outside the plane The PC Interface Module connects your computer serial port to the FS5 receiver for downloading flight information

    FS5 Receiver Detail:

    1) Before you Fly:

    Use the frequency-clear feature to check the airwaves before you even turn on your transmitter. Turn on the FS5. Watch the status LED. It will glow bright red for a second, then it will go out. Watch the LED. If it starts blinking before you turn on your transmitter, there is interference on your channel. Leave the receiver on for as long as you like. Even the briefest signal strong enough to cause interference will activate the frequency-clear feature.

    Check your battery voltage before you take off. Simply press and release the programming button and the LED will blink out your battery voltage (long blinks = 1V, short blinks = 0.1V). Four long blinks followed by 8 short blinks equals 4.8V. You can test the voltage under load by moving your servos while you press the button.

    2) While you Fly:

    The FS5 is fully crystal interchangeable, dual conversion, full range, full performance and is the same size and weight as our Extreme 5. I used a Hitec dual conversion crystal from my 555 receiver for my FS5 receiver without and issues. Sporting improved S.M.A.R.T. decoding with new Digital Signature Recognition (DSR), the new FS5 leap frogs current-generation receivers, yet still works with any standard FM (PPM) transmitter. The FS5 is simply the most secure R/C receiver ever designed. DSR recognizes your specific PPM transmitter signature on start-up and continuously checks for FM shift, number of channels, and valid pulse widths. A DSR anomoly invokes four levels of error correction to eliminate nearly all interference and servo jitter. Once it learns your transmitter signature, the super-fast microcontroller can easily ignore random noise to a level higher than ever before.

    For added security, the FS5 includes fully pre-programmable servo position on all 5 channels in the event of signal loss. Programming failsafe settings has never been easier. This overcomes the normal reluctance of users to go through the pain of programming a PCM system for fail-safe operation. Just press and hold the programming button as you turn power on to enter the programming mode. Move any stick on your transmitter (channels 1 through 5) and set it where you want the flight surface to go in the event that signal is lost completely, as in “my transmitter just died.” As you hold the stick, press the programming button again. That's it. You can repeat the procedure for any or all the channels if you want.

    If you don't want to set pre-defined servo positions, you can still take advantage of improved S.M.A.R.T. decoding with Digital Signature Recognition (DSR) which implements 100% output power to the servos using “last good frame hold” technique.

    FMA 605SB Advanced
    Servo Buffer


    Dimensions: 1.18" x 0.34" x 0.32"
    Weight: 0.10oz (3 gm)
    Current drain: < 1 ma.
    Input: one microlite servo pigtail six inches long.
    Outputs: two 3-pin headers that accept JR, Futaba, Hitec or Airtronics Z-style servo connectors; both outputs are buffered for use as a 2 channel "Y buffer" where required.
    FMA offers an excellent companion to FS5 (and any) receiver installation in situtations where you are using long aileron extensions, etc. in an installation.

    The 605SB servo buffer can be added in-line for each long wire run to the servo. The addition of the FS5 Viewer software and Flight Recorder has given R/Cers the ability to troubleshoot installation and design issues we were never able to see before.

    First fly the FS5 with no buffers. When you land, look at the LED, if it's blinking, it will blink out the number of failsafe events you had during the flight. Don't turn power off or the memory will be cleared! Press the button on the FS5 3 times and it will then blink out the number of bad frames you had during a flight. The objective of course would be to install the buffers (at the receiver) until you minimize failsafe events (should be 0 if your radio is in good shape and tuned properly), and/or a low number of bad frames. This will provide you a very definitive picture of RF performance.

    The FS5 receiver is actually an extremely precise glitch counter. Of course, if you have a real bad installation, you may get several failsafe events and you could run the counter on the bad frames to it's max which is 256. A clean flight should be somewhere in the neighborhood of 30 bad frames or less. It takes 50 consecutive bad frames to go into failsafe. Also, when you're counting bad frames, long blinks = 10 bad frames and short blinks = 1 bad frame. 10 long followed by 5 short would = 15.

    The 605SB servo buffer was designed specifically to provide 100% reliability when interconnecting the Co Pilot (CPD4) with Futaba PCM receivers and is guaranteed to provide smooth operation on both pitch and roll channels If you are having trouble with long aileron extensions or long runs to the elevator or rudder then install this unit between the servos and the receiver to improve radio performance. You might be surprised by how much you haven't been able to "see" before the FS5 technology arrived!

    Combine the FS5 receiver with Co Pilot (FS5A) and you have the world’s first “true failsafe” system. This combination can fly your model out of practically any loss-of-signal situation or massive interference to enhance safety immeasurably and save you a load of heartbreak and repairs. Program receiver failsafe settings for low throttle and rudder turn. Co-Pilot will hold the wings and nose level in a flat, low speed turn giving you time to figure out the problem and/or warn spectators.

    3) After you Land:

    Check the status LED after you land. If you ever lost signal, the microcontroller will notify you by blinking the number of failsafe events during the flight. Need even more precision? With the FS5, you can even check the number of bad frames received during a flight. That’s right, the FS5 is also a sophisticated glitch counter. Thus, you can help your fellow flyers to check for any real or imagined interference at your flying field up in the air where it counts.

    In addition, every FS5 ships with our new Flight Systems Receiver Viewer Software. This software is not required to program or use the receiver, but it’s a great tool for helping you set servo failsafe positions and range test the receiver. The optional software runs on any Windows 98 or newer PC operating system.

    Connect the receiver to any serial port on your P.C. through the interface module, (FSIM1 sold separately), install the software and you instantly have a graphical, intuitive interface to use along with your receiver. The software displays the type of transmitter controlling the receiver. Each channel is displayed using a slide-rule meter showing servo position in real time and failsafe positions if programmed. In addition, the software presents telemetry data received from the receiver in real time, as well as historic data. The program also lists receiver battery voltage, signal strength, data integrity, and much more! Do you have a laptop? Take it to the field with you. After you fly, leave the receiver and transmitter power on, connect the receiver to your P.C., and check to see if you encountered any anomaly during a flight. Sound interesting? The software can be run without connecting the receiver and interface module. It contains a demo program that shows you all major features of the software so you can decide if it's something you might want to use.

    PPM vs. PCM:

    PPM stands for Pulse Position Modulation. In this approach, each servo position is encoded by a specific pulse width. Pulse width for one channel ranges from 1 to 2 milliseconds. A 6 channel transmitter will generate 6 pulses in the output signal. The receiver knows what pulse is servo 1 because of a long sync pulse that lasts 5 milliseconds. A glitch occurs when a stray pulse is introduced to the signal. Suppose a stray 0.1 millisecond pulse occurs in the channel 4 pulse. Servos 1-3 would be positioned correctly, while servo 4 would move to an incorrect position. The glitch gets worse when the receiver shifts channels 4, 5 and 6 down one position because of an extra pulse. The position of channel 5 is now given to servo 6, while servo 6 goes to the empty slot for servo 7. After a single glitch, correct servo positions are restored in the next frame. The 1/50th second wait for the next frame causes little movement of a servo. Since glitches are random, the odds are greater for glitches on the servos connected to higher channel numbers. That is why important control surfaces are on channels 1 and 2.

    Standard PPM receivers have some tolerance for noise. Most of the time, only half the servos receive a big glitch. Smaller glitches will not shift the servos at all. When just one servo shakes a little, a small glitch delayed the pulse on its channel.

    PCM stands for Pulse Code Modulation. In this method, control positions are converted to 10 bit binary numbers before transmission. Each channel requires 10 pulses to represent the numeric position. A glitch in this data stream can dramatically change the positions of all servos on channels following the glitch. However, to keep the numbers readable by the receiver, the transmitter calculates and sends a cyclic redundancy check (CRC) number. The CRC number is recalculated in the receiver and checked to see whether it matches the received channel data. If one or more bits are corrupted, the entire frame is thrown out. This is known as error detection. The PCM receiver then waits for the next clean frame before updating the servos. In a PCM radio system, moderate noise can corrupt several frames in a row.

    Individual pulses are much shorter for PCM because there are so many of them. The higher number of pulses per frame slows down the frame rate. A 6 channel PCM frame will have at least 72 pulses in a frame. One delayed or changed pulse among the 72 will corrupt the entire frame. This is why PCM receivers can lose control and go into failsafe mode. To make things better, some PCM transmitters break up a 6 channel frame into two frames of 3 channels each. This way, only half the channels will be affected by a discarded frame.

    When it comes to glitches, PCM receivers are better then PPM receivers because they catch all glitches. The CRC will never let a glitch through to the servos. On the down side, a PCM receiver will discard an entire 5-channel frame if it finds 1 bad bit among the 50 data bits. In comparision, if a PPM receiver encounters 1 bad pulse in 50, it still has four good 5-channel frames to work with.

    The FS5 receiver combines the advantages PCM (error detection and high noise tolerance) and the advantages of PPM (faster and more tolerant of glitches) to create a higher level in receiver performance. Additionally, the DSR features add increased safety through automatic pre-set and failsafe positioning of the servos.

    The Truth about DSR:

    DSR will not protect you from identical transmitters on the same frequency channel

    When you turn on your FS5 receiver, the Digital Signal Recognition (DSR) is automatic. It checks for the following criteria:

    • positive or negative shift
    • valid number of pulses
    • valid frame length
    • valid pulse widths

    The FS5 receiver is able to store two valid transmitters of the same shift type to support buddy box operation. Once it learns a Futaba transmitter, it will not hear a JR transmitter. Once it learns an 8-channel transmitter signal, it will not hear a 4-channel transmitter; Futaba or otherwise.

    The DSR feature can actually re-construct damaged information. There is digital filtering that will ignore pulses less than 100usec in width. These are usually attributed to interference and noise. This means that these short noise spikes will have no effect on servo motion. Valid information is also tracked from frame to frame. If a frame is damaged, the DSR involkes three levels of error correction to attempt to restore the data. If the data fails to be restored for 50 consequtive frames, the failsafe mode is enabled which sets the servos to either the "last good frame" or the "programmed servo pre-set positions". If a Co-Pilot is connected, the plane will go into a low speed stable turn.

    The worst case scenario is when two identical transmitters are turned on with the same channel setting. The performance comes down to relative signal strength. If you fly close to the interferer, the interferer will attain control of the receiver until your transmitter signal becomes stronger again.

    DSR is always comparing incoming data to the defined criteria listed above.
    A DSR anomoly invokes up to 4 levels of error correction which is how it
    knows when to attempt to repair damaged frame information.

    For the more technically inclined R/Cer, refer to the FMA Flight System white paper (June 2003) in the support section of the FMA Direct Web site.

    P.C. Viewer Software:

    The Viewer Software provides real-time information about the receiver, its failsafe settings, battery voltage, transmitter type, signal strength and failsafe history. It can also be used to record and play files containing this data. Although the Viewer is not required to set up and use the FS Receiver, it can be helpful for troubleshooting. If installed on a laptop computer, the Viewer can be used at your flying field.

    When used in combination with the optional interconnect to computer, the PC Viewer Software can be used to check and record airborne telemetry; battery voltage, interference, and much more.

    Each FS5 Receiver includes free Viewer Software for extended, graphical data readout. Connect the FS5 to your PC with the optional Serial Interface Module, then view transmitter signal strength, servo positions, servo presets, and much more receiver data in real time. The program also records receiver operations for playback at a later time.

    The PC Viewer Software displays a graphical data readout for each channel position, pre-set and failsafe
    information, and real-time receiver performance information

    A comprehensive on-line Help file provides detailed
    information about the Viewer Software
    and the receiver operation

    Optionally, the External Switch/LED Module lets you interact with the receiver from outside the aircraft.

    Granted, you can’t take your computer to the flying field unless it is a laptop so how do you set up the FS5 receiver without the Viewer Software? You can set all the FS5 receiver functions without the Viewer Software through its button and LED, and you set failsafe positions using your transmitter sticks.

    Will the FS Receiver prevent my airplane from crashing? No, the FS Receiver can only move your airplane’s control surfaces and throttle to preset positions when it doesn’t receive a clean signal from your transmitter. This may keep your airplane flying long enough for you to find and correct the problem. For true failsafe operation, use the optional CPD4 Co-Pilot feature.

    If you are installing the FS Receiver in a small aircraft, you may need a shorter antenna. You may cut off part of the antenna without detuning the receiver (a unique feature of FMA Direct receivers). However, reducing antenna length will reduce range. Never cut the antenna shorter than 18” (50cm).

    The increased safety provided from the FS5 DSR features through exceptional interference rejection, frame error correction, and automatic pre-set or failsafe positioning of the servos gives me the confidence to fly my fastest and most precious planes at any R/C event.

    FMA Direct
    5716A Industry Lane
    Frederick, MD 21704 USA
    Web: www.fmadirect.com

    Comments on RCU Review: FMA Direct FS 5

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    The comments, observations and conclusions made in this review are solely with respect to the particular item the editor reviewed and may not apply generally to similar products by the manufacturer. We cannot be responsible for any manufacturer defects in workmanship or other deficiencies in products like the one featured in the review.

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