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DIY 10" sunlight readable plotter
#1
Hi all,

i am using OP since beginning of 2016 with a RPi 2 and RPi 3 and the original 7" display
and the 19design enclosure. I am still impressed about the success of OP.

The 7" display is OK for general navigation. But if you want to display some readings,
compass or wind vane the display becomes too small and it is unreadable if the sun shines
directly to it.

So I was looking for alternative displays, monitors, tablets and so on. I am sure some of
you have had the same idea and you have found some overpriced marine monitors and
nothing else. Having a tablet with waterproof case on deck using vnc is not really what i want.

Time to build your own?

Two weeks ago I have ordered a 1200 nits sunlight readable 10.1" display from china.
Together with a touch-screen and hdmi-lvds controller board. Costs are $110, shipping
via DHL included. The LCD alone is around $55 without touch, pcb and shipping.

My idea is to take a Raspberry Pi compute module which is a RPi without all the connectors
and unwanted electronic that fits to a 200pin DIMM socket like the elderly RAM modules.

The disadvantage is you have to build a pcb with all the electronic needed. This means power
supply, usb hub, hdmi to lvds interface and so on.

The advantage is you get access to all the connections of the RPi. And you don´t need any
cables except the power cable if you include all the electronic you want to this pcb.

The goal is basically a sunlight readable RPi enabled monitor.
 It could be improved by compass, imu and other sensors, as well as interfaces like nmea.

If there is some interest we could start a forum project on this.

All the best,
Chris
  Reply
#2
Do you have a link for that display? It sounds interesting.

I was thinking - rather than trying to builds a system from scratch, what about contacting a company like this and asking them to do the integration?

https://www.aliexpress.com/item/Contact-...b7c854e1-7
  Reply
#3
(10-23-2018, 11:21 AM)abarrow Wrote: Do you have a link for that display? It sounds interesting.

I was thinking - rather than trying to builds a system from scratch, what about contacting a company like this and asking them to do the integration?

https://www.aliexpress.com/item/Contact-...b7c854e1-7

This is the display i have ordered:
https://www.alibaba.com/product-detail/L...7e704adMIK

The brand name is Duobond. The seller is www.aptusdisplay.com

I have ordered the display and touch screen as single parts. Normally they should be optically bonded (glued)
but I want to test if an additional cover sheet works or not. The price for optical bonding is $20. (prototype)

I have tried to upload the datasheet pdf but it doesn´t work for any reason.

My idea for a waterproof enclosure is a 15 mm Forex plate with milled pockets
for the display on the front side and the pcb on the rear side.

Forex is just one brand name for pvc foam. It is very lightweight and easy to mill.

I am member of the maker-space of technical university in Munich so milling or
vacuum forming is no problem. They also have a pick and place machine and a
vapour phase soldering machine.

Cheers,
Chris
  Reply
#4
Sounds like you have the tools to make it happen! One thing - I was searching Google for information about non-RPI DSI displays connected to the PI. The information on this thread https://www.raspberrypi.org/forums/viewt...p?t=188908 seems to indicate that the DSI interface is closed source and proprietary, which might make it difficult to use. As far as I know, that is what is preventing the implementation of multi-touch displays on the RPI (aside from the 7" display that the Raspberry Pi Foundation sells).
  Reply
#5
(10-23-2018, 04:59 PM)abarrow Wrote: Sounds like you have the tools to make it happen! One thing - I was searching Google for information about non-RPI DSI displays connected to the PI. The information on this thread https://www.raspberrypi.org/forums/viewt...p?t=188908 seems to indicate that the DSI interface is closed source and proprietary, which might make it difficult to use. As far as I know, that is what is preventing the implementation of multi-touch displays on the RPI (aside from the 7" display that the Raspberry Pi Foundation sells).

Yes, you are right, it is closed source. 
It is very sad to us but the raspberry foundation have NDA´s with Broadcom to not spread this information.

The RPi supports two MIPI data lanes and one clock lane.
This is OK for 800x480 but for higher resolutions more than two are needed. 

The Broadcom chipset used can support up to four MIPI data lanes but they are not accessible on the RPi.
On the compute modules all four MIPI data lanes are available! Theoretically. In fact they are not supported 
by the kernel software. It took some hours to find out that MIPI cannot be the solution for bigger displays.

Look what nice displays are available that could connected directly but we cannot use them:
https://www.alibaba.com/product-detail/Y...3e43L6NL37

Yes, this is really sad. So we have to deserialise the HDMI output to LVDS parallel signals. This is not a big
deal, there are chips and boards available.

Complete board:
https://de.farnell.com/midas/mcib-14/sch...stViewed_2

Chip from TI:
http://www.ti.com/product/tfp401

The Chip costs less than $10. It comes in a retired qfp 100 footprint that can be soldered by hand easily. I think
a four layer pcb will do it. They are very cheap in china. (pcbway or jlcpcb or...)

My 10" panel is in germany already. It is waiting for customs clearing.

All the best,
Chris

Hi all,

i have no experience with nmea 0183 and nmea 2k hardware.

I am sailing a 20' boat on a lake so there are no instruments
on board.

Can someone provide a schematic, photo or interface description
of nmea 0183 and 2k interfaces?

A photo of an usb enabled interface would be fine. Just to know
what chips are used and what they are doing generally.

I will implement that on the 10" plotter pcb.

Every idea is welcome,
Chris
  Reply
#6
If you are talking about layers one and two - for NMEA 0183 the wired interface is typically RS485 or RS 422. There is a good description on Wikipedia.

Having said that, the protocol interface for NMEA 0183 is now used on just about anything that will transmit data. In OP, for example, you can send NMEA strings (ASCII) on anything that will transmit the data - Wireless or wired ethernet, etc, etc.

NMEA 2000 is a higher speed (250Kb) bus-style protocol that uses non-ASCII binary messages. Because it is a multi-drop bus protocol, it has to include collision detection. It's closed and proprietary, although there has been some success reverse engineering it. Again, have a look at WIkipedia to start understanding it. I'm sure others here have a lot better understanding of how it works in practice than I.

If you are looking for chps to implement RS485/RS422, have a look here https://www.maximintegrated.com/en/produ...ivers.html

If you are looking for chips to implement NMEA 2000 (DeviceNet), Google DeviceNet interface.
  Reply
#7
What is the power overhead of hdmi -> lvds? The typical cheap pcb I tried get very hot, and use a lot of power to do this.

Would you consider other single board computer besides raspberry pi for this? There are many alternatives with much better graphics support, and more powerful. These make a lot nicer chart plotter.
  Reply
#8
(10-24-2018, 09:56 PM)seandepagnier Wrote: What is the power overhead of hdmi -> lvds?  The typical cheap pcb I tried get very hot, and use a lot of power to do this.

Would you consider other single board computer besides raspberry pi for this?   There are many alternatives with much better graphics support, and more powerful.  These make a lot nicer chart plotter.

Hi Sean,

I am not sure. The TI chip is 18 years old so i am pretty sure there is a reason they
added a thermal pad to the tqfp100 package. I will order one of the pcbs from Farnell
to test the chipset together with the display before developing my own pcb.

Regarding other single board computers, if they are available in a similiar board factor
like the RPi compute module it can be done. I will start with the RPi because i already
bought two modules, the development board and some parts like DIMM socket and
SD-Card socket.

Chris
  Reply
#9
Hi all,

the 10" display arrived on monday after one week of customs clearing.

Very sad to say the touch-panel has cracks and the LCD is bended and broken.

I was able to bring up the touch-panel to test an additional acrylic sheet.
It works with acrylic sheets up to 1 mm. I will use a 0.5 mm anti-glaze
acrylic sheet for the plotter.

The good thing is that i know the acrylic sheet will work and the panel can
be optically bonded to the LCD. The bad thing is I have to wait again for
a new setup.

Chris
  Reply
#10
Hi all,

finally i got the new LCD with touch screen bonded!

It looks very nice compared to the original RPi 7" LCD:

[Image: ffef92739c_album.jpg]

The 7" display has 133 cm² and the 10.1" display has 294 cm².  

The 7" RPi display is ok most of the time. At some conditions (sun from behind) i need to shade it.
I am really impressed of the brightness of the 10.1" display and i have no doubt that using it under
strong sunlight will be much better than the 7" RPi display.

The costs for a single lcd was $110 for lcd + touch panel + HDMI controller + cables + shipping.
I paid $20 extra for prototype bonding of lcd and touch panel.

Chris
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