187: Monday 25th April 2011

Today I decided to get the display control simplified so it was easy to trigger events from data sent to the graphic display. In order to do this I needed a development environment. Fortunately the usb interface came with a demo program as a stand alone program, but also as source code in various programming languages. I opted for visual basic in the vb.net domain as there was a vb2008 source code version of the demo already coded. First I had to download the Microsoft dot net framework. That took a while. Then I downloaded visual basic express 2010 from Microsoft. This is free, cool. Once I had done the installations and restarted my PC, I loaded the solution file and there I could edit the source code. This was great as the vb graphic interface development is really easy. So I dragged the bottom of the form down to make it bigger, added buttons for 'Reset', 'LCD on', 'LCD off', 'All points on', and 'All points off'. I also added a 'Toggle data' button this was so I could enable the data set in the check boxes for the digital outputs. I added a timer and set this to 1 second initially and set this to bring on the analogue voltage at the full 5v, then back to 0v after the timer had expired. This was connected to the 'E' terminal on the display to enable the data on the bus. So each button would set up the digital outputs, then bring on the analogue output for a time. I could see this working just fine, so I then set the timer to 10 milli seconds. On the board you can still see a short blip when the analogue output comes on and goes off again. I am using this just like a digital signal really, but I only had 8 digital outputs and they are used for D0..D7 input of the display. This made it very easy to send commands to the display. I installed a simple mechanical button on the prototype board to supply the hard reset voltage when pushed, so I could stop the display from locking me out. I could still only control the display to bring it on and off. I am not sure why this is right now, but I suspect the display is damaged at this point in time. I am not getting the LCD voltage from its on-board DC-DC converter, so I had to supply this using my split rail supply. I get the blue background, but no white dots. I tried the volume control, power control and resistance ratio settings amongst others as well as sending the data to the ram and nothing, nada. I shall wait till pay day and order another display and hopefully that will work. I shall also try contacting the manufacturer and getting them to supply me with a start sequence for the display and some tests to try out. I have the display data sheets (see link in side bar) for the display and the chip set on the display assembly. I have tried the sequence I believe is recommended by Epson and it does not work. This is disappointing, but nothing has been simple so far, and in the typical tradition of this whole project I have typically had 2 of everything, except the Zivan charger and Zapi controller that have worked faultlessly since the day I first tried them.

186: Sunday 24th April 2011

Started off by rewiring the usb interface as the outputs were for open collector transistor drivers and only 0.6v. There was a 5v output to each of the LEDs, so I soldered a connection to a terminal strip with screw terminals. I used a double sided sticky pad to mount this on top of the chips. I then made up a simple ribbon cable with 9 connections, one for each of the 8 outputs from the usb interface and one for ground. This had a strip of pins on the other end so I could plug it into the prototype board. I then figured out which of the bits I need to change to send a 'display on' and 'all points on' messages. The rest of the bits were wired directly high or low. I know this is really crude, but it is just to get the display up and running. I cleared up the desk with my computer on it and moved my prototype board and the display etc. over there with the usb interface. You can see this in the photo below.
After a thorough read of the data sheets, I found a couple of minor issues, but there was a voltage converter inside the chip that was supposed to generate a large negative voltage supply for the display. This was not working and I had the capacitors the wrong way round at one point as the two data sheet showed different polarities. I trust the Epson chip spec sheet as this is the source document. I could not get the display circuit to produce the voltage so I consulted the notes on how to connect an external voltage. I have a split rail supply on the prototype board as well as a separate 5v supply and the positive and negative rails are separately adjustable. I linked the 5v supply ground and the split rail supply ground so they had the same reference. The input voltage needed to be -9v with respect to the positive 5v supply, net effect is -4v with respect to ground. I set the negative rail to -4v and the display flicked on when I powered up. This was progress. I could see like a grid when I sent the command to switch the display on and then another very slight change when I sent the instruction to switch all points on. When I then sent the command to switch the display off, it went right off. I had to use a wired reset low to get the display back, or switch off the power supply. In the photo below you can see the display with a blue square in it. I tried sending some data and it didn't make any difference, but I had to go for dinner and finish up for the day. I have a feeling there is something else I need to do to select the right brightness level or something as I was expecting all the dots to illuminate with the 'all points on' request. I have made progress as the display is visibly responding to my requests. Step by step I will get there. I did a bit of a rewire and I shall use 2 analogue outputs from the usb interface and the 8 outputs exactly as the eight bits for the data. I only need to control the enable signal and the data or control line (A0) that are now connect to analogue outputs. I shall switch these directly from min to max to go from 0v to 5v, so they are just like the digital signals. If anybody has ideas why I am not getting any dots lit up, I'd appreciate your help.

185: Saturday 23rd April 2011

Started work on the graphic display today. First objective was to get the display powered up and basically showing something that I have decided on. I now had the connector board from Tim in USA, cheers buddy. Had a collection of pin strips from when I was making the other displays. In the photo below you can see after I have added one row of pins to the board.
In this photo you see the second row of pins added. This layout is identical to IDE connectors for a floppy disk drive and I had a couple of spare ribbon cables with connectors, so that was a bonus.

In this photo you can see the ribbon cable connected.

In this photo you can see how I handled the other end of the ribbon cable that needed to connect to my prototype board. This shows one of the rows of pins that would connect to the IDE connector on the other end of the cable. As there are two rows then I needed to make two of these and offset the pins to bridge the gap on the prototype board.

In this photo you can see the two connectors I made between the IDE cable connector and my prototype board. I cut the cable as the next part went to a different connector and it made it easier to handle.

In the next photo you can see everything connected. The bits on the left of the prototype board were from another project some time ago. The display is connected to the adapter board and I put a double-sided sticky pad on it's back to stick it to the ribbon cable temporarily. This was for support as the display's own ribbon cable is like a tape. I tried just hooking up the 5v supply, and then adding the other components that were shown in the example circuit on the data sheet. I tried manually wiring the circuit data lines to send some simple instructions, but there was nothing on the display. I still need to add capacitors for the LCD driver circuits and I did not have the right values. I had the right capacitors and resistors for the voltage inputs and have added these already. I need to check what I ordered for this project and see if I should have these parts. Other wise I need to go buy them. I want to finish this up before I try anything else. I decided to just send a control instruction to turn all points on initially. That will prove that the display works. I have a usb controlled interface that I can use to set up a simple bus and send data from a PC to progress from there, then I can work out how to get a PIC chip to do the same job of the usb interface. I was impressed with the Velleman website as I bought the board about ten years ago and I have now misplaced the disk that came with it. I went to the website and within minutes I had downloaded a complete suite of example programs in many different computer languages and instructions on how to install the drivers etc. Another couple of minutes and I had the interface up and running. I now need to clear some space on the bench where my PC is and move the prototype board over to it as I don't want to trail a long usb cable across and then have to keep going backwards and forwards to see what has worked or not.

184: Sunday 10th April 2011

I have had some dialogue with Tim Catellier recently and he has received a connector for me and posted it on as the company wanted $130 to ship it to UK for a $10 part. With this connector I can start the development of my graphic display. I have now had my local supplier send me the wrong connector 3 times and I have asked for a refund. This is my back-up plan and right now I am just waiting for the connector to arrive. It is a 30 way ribbon connector breakout board. This will enable me to access the very fine connections from the ribbon cable to the graphic display. It is a simple circuit board with connection spaced apart so they are easy to solder onto. I shall then connect another bigger ribbon cable to this and then to my prototype board. I can then connect up 9 or 10 switches to manually sequence through the graphic locations on the screen and program them one-at-a-time to generate the static display, then I can start coding up a PIC chip to do the same. Replacing the switches with a PIC chip shall make it possible to run the display and generate the graphics, then onto the measuring circuits. There is a load of mini projects involved in getting this display working, so I hope it will make interesting reading.

183: Friday 1st April 2011

I got my car back on the road today. Still discussing the capacity issue with my batteries, but the supplier has tested them and now they are back on the car. I am still limited to 10 miles, but this is enough to get me to work on a cold day, just. When I was fitting the batteries back I found a broken weld on the battery trays and this was causing that annoying banging noise. I drilled through and bolted it back together and I shall get round to re-welding at some point soon. I cured the vibration on the rear centre stop lamp and and fixed my rear view mirror back on the windscreen and all is back up ready to go. I now have the charger set to provide a float charge after the normal charging cycle to keep it topped up to a good level so long is the cord is connected. This means I don't lose charge while it is sitting after the charge cycle completes, cool. Seems to have the desired effect. Anyway the car is truly silent now, no knocks or bangs any more.