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66

Basically, no microcontroller, even the raspberry pi, is fast enough. The raspberry pi has an onboard GPU that generates the HDMI output. And other than that, the I/O capability of the raspberry pi is incredibly limited - the highest bandwidth interface aside from HDMI is USB. Many of the HDMI conversion projects involve taking another video stream in a ...


48

You would do a BERT (bit error rate test) on the cable. Better yet, look at the eye diagram at the far end of the cable. HDMI is a digital format, which means that there's a threshold effect — cable quality does not affect the picture quality at all until it gets so bad that it actually causes bit errors. "Premium" cable is (supposedly) built to ...


42

Some repeaters have a model for the frequency-dependant characteristics of the cable (which varies with length), and pre-emphasize the signal in the output driver to compensate for those characteristics so that the signal at the far end comes closer to the ideal waveform. Such a driver can drive a longer length of cable than an uncompensated driver can.


27

HDMI cables are tested at an Authorized Testing Center (ATC) and given a certification based on how much bandwidth they can handle (which is to say, how high of a frequency signal they can transmit without the signal degrading beyond some parameters specified in the standard). Signals in a cable degrade. The signal that is input to the cable is not ...


20

No, not directly. Arduinos just don't have the horsepower to do such a task. For this project, I would recommend using a Raspberry Pi. Take a look at this awesome blog post by Joonas Pihlajamaa on using a Raspberry Pi as a Arduino HDMI shield.


13

The specification of the +5V charge is 50mA(according to wikipedia) This is even lower as USB before enumeration(100mA) Any device wouldn't be able to charge , or it will be very slow at 50mA (10x slower than normal USB port at full power, 500mA) I don't think the HDMI connectors are specified for high currents in excess of 0.5A. Furthermore, the +5V is ...


12

The Atlys board uses TDMS inputs, so you'll need a HDMI decoder which takes those inputs and produces VSYNC, HSYNC, DE, and DATA. Xilinx details the DVI encoding and decoding process in a couple of application notes. These each come with example code, xilinx login required: TMDS Video Interface on Spartan 6 Source-Synchronous Serialization and ...


11

If the cables actually conform to the standards specified, then there will be no difference between a "premium" or "ordinary" cable, since the signals in question are digital. However, in reality you may find cables that do not conform to the standard that are advertised otherwise.


10

Yes it can be. But not with just the HDMI standard. There is the MHL http://en.wikipedia.org/wiki/Mobile_High-Definition_Link standard, which uses HDMI connectors. v1.0 has 5V/500mA, V2.0 has 5V/900mA. It's designed to allow a phone or other device to charge from the main device (TV/Projector) while providing a high bandwidth video/audio link. Your phone ...


9

Which pins are not connected? All pins should be connected. But as the TMDS clock and data pins are differential pairs, they run as twisted pair where the shield is connected to ground. It might be that the diff' pair shield is not actually connected to the respective ground pins but to the connector outer shell. I would not count on having 19 separate ...


8

Please see Chrontel's products at www.chrontel.com: CH7035 - TTL to HDMI output. CH7026 - TTL to CVBS. CH7033 - TTL to VGA and HDMI. CH7034 - TTL to VGA. CH7322 - HDMI CEC. Their TTL input supports RGB 8-8-8. 5-6-5, YCrCb 4:2:2, ITU656, etc. I think the Arduino can use their MCU interface to write graphics data to their frame buffer directly. On-chip ...


8

DCC history in HDMI goes via DVI all the way down to VGA. It is implemented in a way that you can simply hook up a standard I²C eeprom memory chip on the monitor side, which are almost as cheap as dirt (AT24C01 and compatible). I2C signal should probably use higher than normal voltages to avoid too much noise Nope. The +5 Volts tell you a different ...


8

GND from Oscilloscope to TMDS_CLOCK- This was almost certainly the cause of your problem. TMDS Clock- is not a ground; it's one half of a differential pair! Connecting it to the ground on your oscilloscope shorted it to ground, which may have damaged the transmitter. For future reference, you should have connected the ground of your oscilloscope to pin 11 ...


7

I'm basing my answer completely on the code and documentation of the dvi_decoder module, and assuming it actually works as advertised. This file seems to be a (modified?) copy of the IP in the app notes Video Connectivity Using TMDS I/O in Spartan-3A FPGAs and/or Implementing a TMDS Video Interface in the Spartan-6 FPGA. These app notes are chock-full of ...


7

I have worked on commercial KVM units and can attest to the fact that they are way more than a trivial exercise to design and get working. One of the challenges in such a design is capturing the analogue waveforms of the VGA/SVGA/XGA/WXGA video signals from an arbitrary computer and converting that into a digital format that can then be processed in the ...


7

Good questions. I have been researching this topic myself recently, and will try to provide some brief answers here. what exactly is TMDS vs LDVS? LVDS (low-voltage differential signaling) is simply an electrical specification for a differential signaling interface, while TMDS (transition-minimized differential signaling) is both an electrical ...


6

Regardless of legality, it still might not be such a good idea. At a minimum you should ensure that nothing bad happens when someone inevitably does try to connect your product to their television (or whatever).


6

ATSC is an all digital feed. As such math, can be used to compensate for weak and / or corrupted signals. This can be done to such an extent that the recovered data may be indistinguishable from the transmitted data. However, as soon as just enough data is lost to make the math not work... poof... the signal appears to just stop. Some ATSC decoders still ...


6

When converting parallel data to serial data, you take a parallel bus running at low frequency, and then clock it out serially at a much higher frequency. Why doesn't it use different type modesules such as 10:1 Gear box ...? A "gearbox" is basically nothing more than a SERDES block, the only difference being that the output is typically multi-bit wide. ...


5

It's not just wires; a cable can't do what you hope for. Since composite AV is an analog and HDMI is digital, you are going to need circuitry.


5

This looks like pre-emphasis. The idea is to pre-distort the signal before transmitting it down the cable so that the eye at the far end of the cable is more open. If you check the pre-distorted eye at the transmitter, you'll likely see something like this with lots of overshoot. If you check at the receiver after a decent length of cable, it should look ...


5

Assuming two cables both conform to the same standards (e.g. HDMI2.0, high-speed, ...) is it possible that a premium cable will outperform a standard cable when using an objective benchmark that measures the quality of picture/audio? No, it's not possible. A digital transmission line is specified to have zero error rate (to be more specific: an error rate ...


4

Just to complement what a previous answer has explained: A DVI/HDMI transmitter can be a good starting point since you can get straight some video. HDMI/DVI Video transmission over TMDS link is logically divided into stages as shown in the Figure 1: TMDS Transmitter Design of Implementing a TMDS Video Interface in the Spartan-6 FPGA TMDS encoders: ...


4

There is no simple MCU solution to do this, but for reference, Texas Instruments DaVinci Digital Signal Processors (DSP) would be a product line that is suited for this. Take a look at the TMS320DM8168, then under the Related End Equipment you can get an idea of what you would need.


4

This is not a trivial exercise, but would be feasible with modern components. I am not sure what you eventual project goals are, but you could bring up a prototype using an FPGA. The Xilinx Spartan-6 family, for example, has HDMI input and output capabilities. The Digilent Atlys Development Board seems like it could support your requirements. The board has ...


4

The coupling could result from a Y-capacitor in the HDMI switch power supply. A Y-capacitor is placed between L-GND and N-GND and often used to filter out common-mode noise and to establish a common ground reference (with respect to "earth"). If the outlet / plug does not provide proper grounding (only N and L connected) and you touch GND on the HDMI cable, ...


4

I suspect HDMI to Cat6 converters don't actually contain baluns, because as you point out HDMI TMDS signals are balanced signals just as UTP pairs are balanced. In the days before HDMI, video signals were generally carried on coaxial cables. To avoid using expensive coax, many manufacturers came up with a method to use cheaper Cat5 cable instead. Since ...


4

HDMI (and HD video in general) requires a very large bandwidth, which implies a fast processor that is capable of generating or manipulating that much data. This excludes microcontrollers. If you want to drive HDMI, the smallest chip that could do so would be a small FPGA, an ARM Cortex A series, or similar. Microcontrollers simply don't have the required ...


4

Any display controlled by an HDMI port is not going to be possible to get working on a "few GPIO pins". You would really need a microcontroller or an SOC with a built in HDMI controller. Keep in mind that such MCU or SOC would also have to have support for connection of SDRAM or DDR memory to support the image source for the HDMI controller. For most other ...


4

Simply, no. HDMI is a quite specialized kind of digital output format which cannot be implemented with a few GPIO pins from ANY microprocessor or microcontroller. There are three major reasons for this. 1) The electrical signals are current-mode, low-voltage differential signals which are quite different from GPIO. 2) The data rate is quite high (up to ...


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