Yifan Lu attempts a PS Vita HDMI mod

OK, so I've just downloaded and installed the notorious Thrill Kill on Adrenaline...

The_Dizzy_Vizzy · 2024-04-26T21:06:05+00:00

Worked like a charm. Instructions say it needs to play on a PS emulator. Adrenaline was my first and only pick. I ran it through PSX2PSP just like any other PS1 game that I've put on my Vita. I was shocked that there was even a Game ID for it, as...

A while ago, Yifan Lu, a member of PS Vita hacking group Team Molecule, posted a technical blog on his website, explaining how he attempted an HDMI mod for the OLED PS Vita and why it didn't end up as successful as he hoped it would be. He also explains the truth about the OLED's "mystery port", whether the Vita has any video output capabilities as well as other interesting discoveries. You can read the whole thing here.

He begins with explaining that the PS Vita's SoC, which is named Kermit, has two MIPI DSI output ports. Depending on the PS Vita model, the first port is connected to a custom 40-pin high speed board-to-board connector (OLED) or a ZIF connector (LCD), which are either connected to an OLED or LCD panel. The second port is only used in development kits and Vita TVs. There it is connected to an ADV7533 MIPI/DSI Receiver with HDMI Transmitter, which is why he suspects that the Vita has those two ports in the first place. He goes on making clear that the Vita's SoC lacks any native support for HDMI/TMDS signaling, shooting down any rumors of handheld PS Vita's with HDMI output capabilities. Remember the second port on OLED models that is often dubbed as "mystery port" and was rumored to be a scrapped HDMI port? That port is actually just a USB host port with a custom physical connector with no video output capabilities.

The pins of the second, unused MIPI DSI port are not routed and therefore it is impossible to use them for an HDMI mod. So Yifan Lu's idea was to intercept the DSI output to the OLED panel and let the same signals drive a custom board that can convert it to HDMI. After successfully soldering wires and locating test points for the desired signals, his original idea was to use the same MIPI DSI to HDMI conversion chip that the Vita TV uses. Unfortunately he had to scrap this due to a number of reasons quoted below:

I wanted to expose a mini-HDMI port on the bottom of the OLED Vita right next to the multi-connector. There is unused space inside the Vita near that region but it is only about 15mm x 15mm. That means all the components I choose will have to be extremely space efficient and therefore expensive.

The ADV7533 only comes in a 49-BGA package which means layout requires at least a 6 layer board with low pitch and drill sizes. This means that prototyping the boards will be very expensive. A normal 2 layer PCB with standard drills can be fabricated for about $10 for each prototype run. A 6 layer board with small drill sizes goes for about $300 for each prototype run.

I do not have the equipment to solder and test small pitch BGA parts which I would have to use to meet the space constraints.

You cannot buy the ADV7533 from standard US suppliers because the part is under NDA and requires you to have a HDMI license which costs thousands of dollars per year.

Because he wasn't going to make profit off these boards, he couldn't justify investing the time and money for this design, which leads to his next approach, cheap MCU evaluation boards with MIPI DSI support from ST. What follows was building a small 15mm x 15mm breakout board to be placed into the Vita and a host board that connects to that breakout board and the MIPI DSI adapter from ST. The host board is also connected to a RaspberryPi which supplies it with power and is used to program the ADV7533 MIPI/DSI Receiver of the Vita.

Next task is communicating with the ADV7533. Since it is under NDA, an official programming guide is not available to the public. So Yifan Lu looked at various open source implementations and was able to write a Python-based configuration sequence that allowed him to successfully build communication with the ADV7533. Under normal circumstances, video should show up now, but it didn't. Trying to figure out what's wrong, he brought out his trusty oscilloscope. An oscilloscope is a device that analyzes various signals and displays them as waveforms to observe changes in voltage. To summarize his fairly technical observations, he concluded that there is an issue with the ADV7533's clock and data lanes entering HS (high-speed) and LP (low-power) modes and the lack of any logic to handle clock lane LP transition. His tests showed that on the OLED Vita, it is not possible to have the OLED and HDMI working at the same time, but implies that it can be fixed with a hacked PS Vita. However, as he doesn't want to limit the adapter to hacked PS Vitas, he tried to find another solution but unfortunately without success.

Nonetheless, Yifan continued this project to hone his design skills and in the end was able to redesign his board and made it programmable without a RaspberryPi. He says he doesn't plan to pursue this project any more than that, but open sourced his designs in case others want to continue where he left off. In that case he provided a couple of tips to start:

If you only care about hacked Vitas, you can try to get the existing design to work with a custom driver that sets the auto clock configuration to output to the screen or to the external adapter. You can also try to find the test-points on a Vita slim. Finally, if you want sound, you need to find the an I2S output somewhere.

If you want to try another part, you can look at one of various MIPI DSI to eDP chips (for example this) and chain it with a DP to HDMI chip or with a DP cable. Make sure the chip you’re using supports LP mode!

If you want to design your own part using a FPGA, that might be the best route but you need to make sure your FPGA supports MIPI D-PHY, which most likely it won’t and you’ll have to make a level translation circuit. I think this is what the existing Vita video out mod does.