My quest for a cheap LCD for Neato XV!

[Tris]

For a while now, I've been searching for a reasonably priced Binky UI board so I can replace my XV Signature's blank LCD. The cheapest one I found would cost $92 to buy and import into the UK! No way was I going to pay that much, so I hunted around for info on the LCD board with the idea of finding a compatible LCD module and (hopefully) a cheap fix.

I wanted to share my experience and progress, so here goes...


The site "xv11hacking" (https://xv11hacking.wikispaces.com/XV-1 ... nformation) had revealed the part number and manufacturer for the OEM LCD (Golden Vision GVLCM128128G 13572A) and deduced that the LCD controller used was most likely the Sitronix ST7541.

In the "Neato XV11 Button problems" thread on this site (http://www.robotreviews.com/chat/viewto ... 20&t=19141), snoozy had produced a pinout for the Binky UI board's connector and worked out that the interface to the motherboard was I2C.


Based on the above research, these are my criteria for a potentially suitable LCD:

1. Cheap!
2. Easy to get - no minimum order value or quantity
3. 128 x 128 resolution
4. ST7541 controller
5. I2C capable
6. Not physically bigger than the original in any dimension


After a fair bit of searching, I found just ONE match that satisfied all requirements, the EastRising ERC128128FS-3:

http://www.buydisplay.com/default/2-2-i ... k-on-white

ERC128128FS-3 Drawing

After studying the datasheets and comparing their sample schematics to the Neato board, I was able to match the pinout to the PCB traces and confirm I2C configuration.

LCD Connections

As these EastRising LCDs are really cheap ($6.11 including connectors), I took the plunge and ordered a couple to experiment with. The cost for two LCDs with shipping to UK = $18.40.

The long wait for the LCDs to arrive from China gave me time to work out the best physical connection between the Neato PCB and the 31-way 0.5mm pitch FFC on the LCD, but more on that soon...

Old vs New LCD

To be continued...

[Tris]

The new LCD already had double sided adhesive strips applied to the back so mounting it was straightforward. There are no pins on the backlight to align the new LCD so I took great care to stick it to the PCB straight and dead centre of the printed outline:

New LCD stuck to PCB

The new backlight is connected with a pair of flying leads, as opposed to soldered pins on the old LCD. I cut back and soldered the wires to the old backlight connection points to make use of one of the existing current limiting resistors (R11 in the pic below). Red goes to the 5v supply and black goes to any one of the remaining three holes:

Backlight Connection Front

Backlight Connection Rear

In the next update, I'll be dealing with interfacing the LCD's 0.5mm pitch FFC to the Neato PCB with one of these handy $3 adapters:

0.5mm Breakout PCB

Stay tuned...

[mfortuna]

Nice job so far! I like that breakout board you found. I may be able to use that on a project I am doing at work. The one I originally found was much more expensive.

[Tris]

I decided to replicate the Neato circuit on my breakout board in order to reduce the number of wires that are needed to connect the board to the Neato PCB and keep things tidy(ish):

Work in progress

The additional SMT resistor and capacitors were lifted from scrap PCBs I had laying around:

Circuit done

Only four connections are needed now; +3.3v, GND, SCLK and SDATA.

PCB Connections

Now it's time to mention an earlier observation. I had noticed that the pinout of the new LCD was in reverse order to the old LCD. Also, the ST7541 chip was mounted on the underside of the new LCD glass, instead of on the top. In hindsight, it shouldn't have been such a big surprise to me when I powered it up for the first time and...

It's life, Jim, but not as we know it...

Bingo! I now have the world's first and only backwards Neato.
At least it worked on the first try!

So, the next update will be about trying to lift and flip the LCD without breaking anything. It's a good job I bought two...

[shirgal]

Tris,
Excellent job so far

[Tris]

Flipping the LCD over was a success - the LCD is stuck to the backlight with two very narrow adhesive strips. The LCD lifted quite easily and the adhesive remained on the backlight, which was a bonus! I flipped the spare LCD first and tried it out, then did the one on the Neato PCB:

Spare LCD Flipped

Neato LCD Flipped

Now there are two new problems to overcome:

1. The transflective layer that bounces ambient light back through the LCD is now on top. This makes the display harder to read and almost impossible in bright ambient light, like in the pic below with camera flash:

Light Reflection

2. The LCD cable is also flipped and the contacts are now facing down and in reverse order. I plan to stick the adapter board to the Neato board, which is not possible if it's upside down.


Time to make a second "mirrored" adapter PCB and go about removing the transflective layer...

[Tris]

The transflective layer came off OK, I just had to peel it off carefully.

Removing Transflective Film

The display looks perfect now:

Film Removed, No Flash

Film Removed, With Flash

Just the second adapter board to finish and install now, hopefully it'll all fit back together!

[TechGuy]

Great job.

Can you stick the transflective sheet peeled off the (now) front side to the other side of the LCD panel?

[Tris]

Unfortunately not. Peeling it makes it crease, curl up and also ruins the adhesive.

It's not really required as the LCD is always backlit when in operation.

[glnc222]

How is it connected to the Neato system board?

[Tris]

Look at post #4, 3rd photo - 4 wires from my adapter board to the solder pads for the old LCD.

[glnc222]

I mean the clamp connector on the system board for a ribbon cable. Is it removed?
[edit] Is the breakout board inserted in the system board connector? Photo limited.
[edit]I see -- all photos are of the LCD panel board, connections to the display component.

[Tris]

Ah, right.

No, the original cable connection from the main board to the UI board is retained.

[Tris]

MkII adapter board is complete. I scavenged a suitable ZIF connector from old CDROM drive:

MkII Adapter

I applied a layer of Polyimide tape to the underside of the adapter to prevent short circuits, then added double sided self adhesive foam pads:

Installing

Adapter stuck in place and insulated with more Polyimide tape:

UI Reinstalled In Case

Robot reassembled and ready for testing. Let's see how long this cheap LCD lasts!

Job Done!

[glnc222]

Breakout board Adafruit 1492 https://www.adafruit.com/products/1492
Digi-Key part no. 1528-1096-ND http://www.digikey.com/product-search/e ... uit%201492
Adafruit also shows ribbon cables.

For more such repairs see Mods & Repairs list top of main forum page, now linking this thread.
Links also posted to French and German Neato forums.

[mfortuna]

Nice work! Hopefully others with bad LCDs will benefit from this well documented repair.

[Tris]

I forgot to say, I had to break off these two plastic "tabs" before the case would fit back together. Also, the 5 way cable stretched across the area with the tabs needs to be tucked down and to the side out of the way:

Remove these tabs and relocate that cable!

The above pic is of an XV-11 Cruz taken from Google images as I forgot to take a pic. I didn't want to strip my bot down again, but I'll update the pic if I do!

Speaking of Cruz, I've been looking at some great photos from someone who has attempted to remove an LCD from a VR100 Cruz to fix a Binky. It looks like Cruz uses exactly the same LCD module as Binky, but is configured to run in 4-wire SPI mode instead of I2C.

https://imgur.com/a/dLFsn

[glnc222]

Different, related LCD issue: different connectors for oldest Rev.113 Cruz system boards, with clamp and newer Rev.64 Binky system boards with header pins.

Can any breakout board and available connector adapt an old LCD board to the newer system board? Presently when replacing an old system board with a new one the LCD board would also have to be replaced for the different connector.

[Tris]

It certainly looks doable, but tricky. The two versions appear to interface to the buttons, LCD and backlight differently:

Differences between Cruz and Binky UI boards

Cruz Vs Binky UI.jpg (45.75 KiB) Viewed 57704 times

It would involve modification to the UI PCB and you would have to...

1. Add the relevant resistors to the switch outputs to recreate the voltage divider;
2. Re-wire the LCD for I2C;
3. Remove and jumper across Q1 so the CPU board can drive the backlight directly.

I think the LEDs are driven in the same manner but I'm not 100% sure.

[Hipsi]

You're a freaking legend! I'm so glad I've come across this thread. I found this breakout board, with a connector already attached, just to save a little hassle.
http://www.hotmcu.com/fpc-05mm-pitch-40 ... p-122.html

I'm going to grab these bits and undertake the same project. Really bugs me that the lcd doesn't work.

Thanks again for your hard work mate!