Mr.RC-Cam

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About Mr.RC-Cam

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    R/C, FPV, Embedded Programming, Electronic Design.

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  1. FWIW, video level issues, like the bad FR632 vRx in this discussion, affect other FPV systems too. Not everyone recognizes that their video image's problems are due to incorrect video levels; Instead they blame other things. The only way to know if the video level is correct is to measure it. That's easier said than done! The problem is caused mainly by the lack of respect for the composite video standards. These industry documented specifications are often ignored to save manufacturing cost, other times it's due to the ignorance of the video circuit designer. Our cheap imported FPV products have been big offenders of this. To help combat the problem I've created a DiY built tool to check the video levels. It can also be used to calibrate the video level. The project is simple to build and replaces expensive/complex test equipment. Any FPV hobbyist that cares about their video signal level can now easily check it. Details are published here: https://www.rc-cam.com/forum/index.php?/topic/4126-diy-fpv-video-calibration-tool-low-cost/
  2. Firmware flashing comes next. So come back soon for the details!
  3. Assembling the vTx and vRx video generators requires basic soldering skills. And in case I have not been clear, there are two (2) MinimOSD's used in this project. First you need to connect some ground and power pads that are on the two MinimOSD boards. Just add a blob of solder across the pads shown below (Grounding pads on bottom side, SJ2 pads on component side). Some suppliers have already done this for you, but if the pads are not bridged then you must do it. The new firmware (to be flashed later) includes an optional battery voltage monitor feature. This requires adding a jumper wire, as shown below. If your MinimOSDs are the old/original version (not "KV Team") then the voltage monitor feature will require adding some 1% 1/8W resistors, as shown below. Each boards' Power and Video connections are available on the stacked 3-Pin headers. The pins are labeled on the bottom of the MinimOSD board. The vTx OSD only uses VOut and +12V power pins. The vRx OSD needs VOut, VIn, and +12V. I used 3-pin servo plugs to connect the MinimOSD boards, but direct soldering can be used instead. The video connectors you use are up to you. I installed RCA phono panel jacks and made some simple adapter cables that connect them to the FPV system. How you do this is your choice. As a reminder, the vTx's MinimOSD does NOT use the VID-IN signal, so be sure to omit it.
  4. So it's time to gather the parts to build this cool tool. As mentioned before, you need two video target pattern generators; One for the FPV vTx and another for the vRx. The target patterns are provided by low cost Arduino based FPV OSD boards. Here's the Parts List: 2 pcs, MinimOSD (KV Team version recommended). Approx $8 USD each on eBay and AliExpress. To flash the custom firmware you'll need one (1) of these: FTDI FT232RL USB to TTL Serial Converter (6-Pin version) for Arduino. Approx $3 on eBay and AliExpress. Keep in mind that there are several similar looking Chinese clones of the MinimOSD on the market. I recommend the "full size" board that has the KV Team Mod (built-in voltage attenuation resistors). Here is what the KV Team version looks like: How to tell the difference in board versions: The KV Team version will have the JP6 8-Pin header area (8 empty solder pads across the top). See photo above. It's important that both OSD's have identical video signal characteristics. Therefore, I recommend that you purchase both boards at the same time from the same supplier. This should reduce the chance of any component variations that might cause unmatched video levels. You can use your existing 7-12VDC FPV batteries (3S LiPO is fine) to power the boards. No other components need to be purchased. But if you want a power switch, A/V connectors (I used RCA phono chassis panel jacks), or plastic enclosure, then feel free to add these things to the shopping list. Although you can simply protect your OSD board with some heatshrink or duct tape, the 3D printed plastic case gives it a professional appearance. Here's the STL files for it. Case Base: case_base1.stl Case Top: case_top1.stl Case Hole Plug: case_plug1.stl Printing recommendations: ABS filament, 35% infill, 3 layer shell, 101% size scaling (shrinkage correction). There's room for a mini toggle power switch, Alkaline 9V battery, and RCA panel jacks. The "Case Hole Plug" file is a small piece that covers an unused RCA mounting hole on the vTx pattern generator (Vid-In is not needed on the vTx side). Here's how everything fits inside my vRx target generator: BTW, the vTx looks the same, but has only one RCA jack.
  5. The magic behind the Video Cal Tool relies on our eyes' ability to easily see relative differences in brightness during a side-by-side comparison. The basic test setup is as follows: (1) A monochrome video overlay provides a video reference (comparison) target pattern on the FPV display (goggles or monitor). It is directly connected between the FPV vRx's Vid-Out jack and the display. (2) A second video source provides a mating target pattern. It is directly connected to the video input of the FPV vTx (the FPV camera is removed). During the test the vTx's pattern is superimposed on the vRx's reference pattern. The mating target sets will have matching brightness when the FPV system's video level is properly calibrated. To account for the display's dynamic range and/or gamma behavior, one target set has 80% luminance and the other has 120%. Here is the vTx test pattern: Here is the VRx reference pattern: Ok, so that's what the vTx source and reference vRx targets look like. But now you're asking, how do you use them to measure the video signal's level (amplitude)? Answer: Your eyes are the "measuring" equipment. When I say using the tool is EZ, I mean it! During the test the T-target pattern fills the empty inside area on the R-target. Properly calibrated video level appears on your display monitor as shown below. But if the two interlocking patterns do not blend together (brightness not the same) then the FPV system's video level is incorrect. Here's two examples: What do you do when the brightness does not match? Fortunately this problem can be fixed on most analog 900MHz / 1.3GHz / 2.4GHz FPV video systems since they usually have an adjustable video level POT (variable resistor) in the vTx or vRx. Unfortunately modern 5.8GHz systems don't provide a calibration POT, so if the test fails you will be out of luck. But at least you will know that your 5.8GHz system has a video level problem.
  6. FPV Video Calibration Tool: DiY -- Low Cost -- EZ to use. The calibration of our FPV system's vTx / vRx composite video signal level (amplitude) matters a LOT. Unfortunately many are incorrectly adjusted out of the box. There's a number of reasons for this -- marginal designs, poor manufacturing QA, compatibility problems due to brand mixing by end users, cheap component drift, and just plain bad luck. Hold on you say! You are convinced that your system's video is fine. But perhaps that's wishful thinking. Here's the cold hard reality -- Many FPV systems have marginal video levels and this invites problems that are often blamed on other things. For example, the random "weak signal" blackouts we all hate are not always directly RF signal related. Poorly calibrated video levels will cause those random blackouts too. Plus a host of other image quality problems that are simply victims of marginal video levels. Checking the composite video signal normally requires an oscope (oscilloscope). Ideally a test pattern generator is also used to provide the 1Vpp standard video signal that is measured with the oscope. Not many hobbyist have access to this equipment or know how to correctly perform the measurements. So I experimented with video level testing using simpler tools than a oscope. My goal was to have something that worked well, but was cheap and simple to use. After a bit of head banging a clever DiY solution was born. How does ~$20 USD and a couple hours work sound to you? Yes, really. Here's what my DiY FPV Calibration Tool looks like. Spoiler alert: Inside the small 3D printed plastic box is a $8 eBay circuit board and a 9V battery. To calibrate a FPV system you'll need two of them. Both boxes will use identical hardware but with different firmware. Oh you guessed it, Arduino is involved. Come back soon. I'll show you how to build and use it. Your FPV system will thank you. The world will be a better place.
  7. You will connect your FTDI serial adapter directly to the OSD whenever you flash new firmware or character files. So that means the canopy would come off. I understand the concern about convenience. Although not shown in the photos, I went the extra mile and added a pigtail connector to mine that hangs outside the canopy for easy re-flashing. But for me it's a wasted feature since I've never have had to use it.
  8. There are no wires there, it is an empty connector. You will need a mating JST 6-pin 1.25mm pitch pigtail plug (avail on eBay). The 2 Watt rating is physically too big. I suggest 1/8 Watt axial (avail on eBay). Your USB serial adapter will have a 3.3V/5V jumper on it that chooses the optional voltage that powers the user's circuit. It will be either a soldered jumper pad or a 3-pin header with plug-in shorting bar. Either case, the adapter's PCB will be labeled so you can make the choice. When used with typical Arduino boards the voltage jumper is normally set for 5V. But when programming the OSD, which needs clean/healthy 5.0V, it is sometimes necessary to power the OSD from a more reliable source. So the jumper must be removed in this scenario. There's nothing magic about it, it is the same thing as isolating the OSD's 5V power input from the USB adapter and then powering the OSD from an external source.
  9. Just my opinion, but I'd recommend using the built-in VReg or another dedicated VReg to power your extra stuff. This will reduce the burden on the Headplay VRegs. EDIT: BTW, if you are connecting external power to the 2S-3S input then keep in mind that applied voltage needs to be at least 6V for the internal 5V VReg to work correctly. This is not unusual; The Autoscan feature on many FPV receivers is subject to this issue. Convenient in principal, when autoscan is used it can be fooled by your nearby 5.8GHz vTx's strong RF signal and cause an adjacent Rx channel frequency to be chosen instead of the exact match. The big surprise occurs later -- The video image will look fine until your model is 25-100 meters away. Then the mismatched channels will drop the video link like a rock and you'll be flying blind. Avoid this by setting it manually to the correct frequency that matches the vTx.
  10. The thing about the Chinese FPV board cloners is that they rarely know what they are doing. On top of that, the eBay sellers are clueless too. It's double jeopardy on our end due to poorly designed copies and error prone published specs. I looked at the photos shown in your eBay link. Assuming that you received what is shown there, I highly doubt their claim that it was designed to run on 3.5-5.5V. Evidence suggest that it has a onboard 5V VReg that expects 2S-3S. See my comments in the images taken from the eBay ad: There's also a design error on the VReg. The VReg IC's input leg has a 1K resistor on it that appears to connect the 2S-3S power input to ground (not sure why they did that). There should be a small value cap (0.1uF is typical) directly on the VReg's power-in leg to ground to ensure VReg stability. FWIW, because they used a linear VReg be mindful of excessive heat / thermal shutdown if you power it with a 3S. If it gets blazing hot on 3S you might be better off with using 2S instead.
  11. The first time I powered mine the OLED showed English text and the menu nav switch worked. Edit: There is something wrong with your board if it does not accept 5.0V. But regardless, the typical "5V" Mag buzzer will work on less than 5V, some buzzers will continue to work as low as 3V with a slight reduction in volume. Furthermore, the buzzer is optional, so don't worry if you decide to not install it.
  12. I pulled my Rodeo apart and checked out the Microphone problem. From what I can see, Walkera didn't include a preamp on the Electret mic. So the mic's signal doesn't have enough drive. That's why the monitor's audio is barely heard even at maximum volume. You'll need a amplified Mic that provides a common "line level" signal. For example, upgrade the camera with one that has a Mic in it or use DPCAV's Tiny-Mic. Or build a DiY electret mic using a OpAmp with 5X gain. Here is where you can find the Audio Input on the vTx PCB: The two circled resistor pads are the audio input. They are connected together, so you can use either. But depending on the amplified mic, it may be necessary to remove/discard those two 0402 sized resistors. If not already provided on the Mic, the Mic's audio signal should be AC coupled to the vTx with a cap (0.47uF is fine). The stock mic can stay (just ignore it). The Walkera's audio RF sub-carrier is 6.5MHz; Your vRx will need to be compatible with it.
  13. Great! Those two resistors are 5V i2c pullups. The Rodeo Buss is 3.3V! So to avoid harming the i2c it is wise to remove the two resistors BEFORE installation. No noticeable difference in flight time. That won't happen until the next time I need to dismantled the Rodeo. On the first baro test be prepared for the unexpected. With the factory/stock PID values mine shot up like a rocket when I set the alt-hold switch. So I suggest starting off with reduced settings (or try my posted values) and tweak them until you are happy with the hold performance.