1
Show Posts
This section allows you to view all Show Posts made by this member. Note that you can only see Show Posts made in areas you currently have access to.
Messages - Royalblu
2
Project development, ideas, and suggestions / Re: Advanced USB LCD Backpack
Touch screen controller or basic 5-6 button feedback?
James
3
Project development, ideas, and suggestions / Re: Designing jigs for programming and test
The programmer is a keyfob like device with a 2x3 IDC connector on the end. Inserted in it is a 2x3 pin header with .1" spacing. The pins on the header are about 1" long. We have squeezed the pins together at the end so they fit in the 2x3 holes on 2mm centers. Squeezing them this way puts just enough spring on them to make a very reliable connection. We have programmed hundreds of boards this way without any problem. We have a 2mm to .1" adapter for longer term programming.
Another method we use for testing LCD modules without connectors is to stick a long single row pin header in the holes where they would normally be soldered. Then just lean them to one side and use the spring of the long pin to keep tension against the hole. This requires you to keep it in your hand but still only takes a few seconds.
Hope this may help.
James
4
Project development, ideas, and suggestions / Re: USB LCD BACKPACK
Almost every alphanumeric LCD I have ever worked with can be made to work with a supply of 3.3V. The thing you have to work around is the contrast voltage.
The spec. of the contrast voltage is Vdd-Vo. For most standard temp LCD's that ends up being 5V-4.9V=.1V for example. That is why tying the contrast pin to gnd usually works just fine.
But if you run at 3.3V, 3.3V-4.9V= -1.6V. So putting a -1.6V on the contrast pin will give you the same contrast as if driven from 5V.
If I have customers who want to do this I usually recommend a cheap and dirty PWM off a processor pin to create a charge pump or just drop a 7660 on the board.
Michael, when you say the really large displays exceed the USB 500mA limit, are you referring to just the logic or with backlight?
One company I worked for had a 4x40 alphanumeric display that was almost 12" long and had a .5" high character. The logic still ran fine at less than 50mA, but the backlight was the real power hog at 5V and 2.2A.
James
5
Project development, ideas, and suggestions / Re: USB LCD BACKPACK
I ran upon a product in the Mouser catalog from company JEM Innovation. It is marketed as a LCD tester that uses a PC keyboard to send data directly to an alphanumeric LCD. What is so amazing though is all the different connector options you have on this board.
If you are up to putting more connectors on, then this may be a good pattern to follow.
I offer also a couple of other observations:
Some LCD's will require a negative voltage on the contrast pin, especially wide temp and graphic parts.
If you do want to use this board for driving graphic displays, you better check the contrast voltage requirements.
If you were to use a GAL or something instead of the 595's then you could easily reconfigure the pinout for your needs.
Many smaller graphic COG modules have their power needs all taken care of on board, but again the pinouts are all over the place as well as connector configs.
James
6
Open Bench Logic Sniffer / Logic Sniffer mention in Nuts & Volts
Congrats