TW8844 Eval Kit Quick Start Guide

Learn how to assemble the hardware, change video source and demonstrate the MIPI loop back feature on the TW8844 evaluation boards.


Hello, my name is Stephen Wickland, Principal Applications Engineer for Intersil Corporation, and I'm here to introduce you to the TW8844 evaluation kit. The kit comes in a large box containing all the hardware pieces. Inside, the main piece is the evaluation board itself, two daughter boards, and there are two optional displays. So either a 1920 x 720 display, or another option, our dual 1280 x 720 displays. Looking a little closer at the evaluation board, we have two CBVS inputs, we have two connectors, which the daughter card clips into, and the daughter cards deliver both TTL and LVDS signals. We have a communications port, and a dongle not shown, that will convert USB to I2C to communicate with the chip. On the output, we have a single connector that connects to either the dual displays or the single LCD display.

For the next section, I'd like to show you the assembled evaluation kit. As mentioned before, we have two RCA jacks for CVBS input. We have two daughter cards connected to HDMI. They're converted from HDMI to TTL on both cards. If we wanted to use the LVDS input, we would merely unplug and plug the second connector into the board. We have our dongle for communication to the chip, USB plugs here, and it interfaces to the evaluation software. On the output, we have a daughter card from the single connector through two ribbon cables to our dual display setup. For the wide display, we would still have two ribbon cables, but only a single LCD panel.

For the next section, I'd like to show you live video. I have two separate 720p video sources connected to the daughter cards that I'm displaying now. Currently we're only looking at one of the video sources on both screens. I'm gonna show you how to change this with the software. First, I'll bring up the two scalers. You can see the scale. And I'll bring up Scaler 1, and bring up Scaler 2. Let me move these so you can see them both. The "R" is read, and we'll read all the register settings. Move to Scaler 2, and read all the register settings. And you can see number two DTBA is selected on both scalers. If we'd like to switch to the second video source, I'll just move to source four, and now we have two separate video sources displayed on the screen simultaneously.

Before we get into the next demo, I'd like to take you through the block diagram because the path for the video is a little bit complicated. The video comes in through DTBB, goes through the scaler, and goes directly out to display number one. Display one shows essentially the incoming video. Also split from the input path is the red path that goes to the MIPI output block. It converts to MIPI. It comes out to the motherboard where it's converted from MIPI back to TTL. The TTL is then fit into the other input through the red path in the chip, out to display number two. So display two shows you the MIPI converted back to TTL. We are now displaying the video talked about in the previous block diagram. I wanted to highlight the OSD feature, which you see at the top of this display. This is a feature of our TW8844 chip. The board recognizes that this is a MIPI loop back setup. The firmware detected it when we powered up. It's telling us that on the left side what kind of video input source we have, and on the right side that we have a MIPI loop back.

Moving back to the computer, I'm now showing the standard TW term. I'm gonna bring up the MIPI tool, and like we did before, I'm gonna read all the registers. For convenience I'm gonna convert all the values shown to decimal. In the center, we have all the different MIPI timing settings, and if you notice, it says our MIPI sourse is DTB one.

One convenient feature of the software is the ability to show deltas. By clicking here, any register changes I make will be highlighted. So we can change a register either with an arrow key up, and you see it change from six to seven, and that field is now green. I could make another change, and it's also highlighted. If I hover over that register setting, you can see what register I programmed, and you can also see the reference value I started with. The reference value is six, I change back to six, the reference value was five here, and I'll type five.

So that wraps up out demo for today. The TW8844 is extremely flexible, it can handle many other video resolutions, it can handle other video sources. If you'd like to order an evaluation board, go to the TW8844 product page. Thank you.