EEVblog Electronics Community Forum
EEVblog => EEVblog Specific => Topic started by: EEVblog on April 13, 2018, 11:31:30 pm
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Part 2 of designing your own custom LCD display.
Looking at the manufacturers datasheet for approval, and test design considerations.
https://www.youtube.com/watch?v=10D5jpO45Lo (https://www.youtube.com/watch?v=10D5jpO45Lo)
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EEVblog LCD tutorials series - forum links
1: https://www.eevblog.com/forum/blog/eevblog-1044-lcd-technology-tutorial/ (https://www.eevblog.com/forum/blog/eevblog-1044-lcd-technology-tutorial/)
2: https://www.eevblog.com/forum/blog/eevblog-1045-how-to-drive-an-lcd/ (https://www.eevblog.com/forum/blog/eevblog-1045-how-to-drive-an-lcd/)
3: https://www.eevblog.com/forum/blog/eevblog-1055-how-to-design-a-custom-lcd/ (https://www.eevblog.com/forum/blog/eevblog-1055-how-to-design-a-custom-lcd/)
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I did a mapping of the LCD driving signals for a scale to understand how it was done for the 4 x 12 matrix of this scale. I came up with the table below.
The top table contains a summary of all the signals, displayed in Volts with respect to ground.
The four tables beneath are an expansion of that, showing the voltage across each segment
When a segment is NOT to be turned on, it has an alternating voltage of either (a) +1 and then -1 or (b) -1 and then +1. What is interesting is where you see (a) or (b)...
NOTE: This is for a simple scale LCD - NOT Dave's custom Microsupply display!
(https://www.eevblog.com/forum/blog/eevblog-1074-custom-lcd-design-part-2/?action=dlattach;attach=411961;image)
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@ dave:
i was wondering about the mechanical diagram of the display that you show at the end of the video: there is a "viewing direction" arrow pointing at the _solder_ side (back side) of the display. i would have expected that arrow to point onto the top side (front side) of the dispaly. what am i missing here? :-/O
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Does the DC driven LCD still works?
Alexander.
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@ dave:
i was wondering about the mechanical diagram of the display that you show at the end of the video: there is a "viewing direction" arrow pointing at the _solder_ side (back side) of the display. i would have expected that arrow to point onto the top side (front side) of the dispaly. what am i missing here? :-/O
That arrow is referring to the main front-view, not the side-view. It indicates the 6 o'clock bias of the view angle.
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Looking good! Seems capable of some limited branding at boot-up as well :-+
*edit - Oops! Forgot a letter..
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Does the DC driven LCD still works?
Alexander.
Yes, amazing it still works :-+ I guess you were sleeping IIRC, Dave mentioned that during the live scope draw
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There are some STM32-s with segment LCD controllers, going up to 8x40. For example, STM32L151. Perhaps it is better to drive the LCD directly from the uc? The LCD is 8x30 (actually 8x29 as pins 18 and 27 could be tied together). If the LCD manufacturer would fit the design into 8x28, there would be even more STM32-s.
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Dave, would be nice if you would sell ithis LCD separately, could be used in many different DIY PSU or electronic load projects!
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There are some STM32-s with segment LCD controllers, going up to 8x40. For example, STM32L151. Perhaps it is better to drive the LCD directly from the uc? The LCD is 8x30 (actually 8x29 as pins 18 and 27 could be tied together). If the LCD manufacturer would fit the design into 8x28, there would be even more STM32-s.
Dave did actually discuss this very aspect - and made two very significant points as to why a separate LCD driver was beneficial...
The first was that you could place the micro and the LCD driver wherever was optimal for each on the PCB and you only had 3 traces for SPI to route between them. The second was the cost for two separate chips against that for an integrated unit.
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Does the DC driven LCD still works?
Yes.
Likely impossible to say if any "damage" has been done though.
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Can you let us Know who you are using for this Dave (LCD manufacturer)......I have a little job I need doing and these guys seem good to deal with...... also will they copy existing LCD screens? I have a heap of the same gear all with bleeding displays that are no longer supported......?
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Mr Jones,
Several months ago I tinkered a bit with HOLTEK HT1621.
I encountered some "traps for young-players" I would like to make you aware of:
1. Clock speed - in case of 3V3 operation, the clock speed must be reduced below 150kHz in WRITE mode and below 75kHz in READ mode, otherwise the driver chip remains unresponsive.
2. Writing a command code requires 13-bits long word to be sent to the chip and in block write mode a 9-bits long command/address word needs to be sent prior the data. This may render SPI module in your system controller useless for this task and may force you to write an appropriate bit-banging code (which happened in my case).
Hope this will shorten your "time to public"
Apart of these, HT162x is an excellent choice and it is cheap as a dirt and that prevails.
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Can you let us Know who you are using for this Dave (LCD manufacturer)......I have a little job I need doing and these guys seem good to deal with...... also will they copy existing LCD screens? I have a heap of the same gear all with bleeding displays that are no longer supported......?
Harb, check back in Part 1 - Episode 1055 (How to Design a Custom LCD)
here, he didn't want to recommend anyone just yet (https://bit.ly/2qtRdun).. but he shows us how easy it is :-+
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No worries Cliff........
I have a stack of Radio Gear in big pile, that all have bleeding displays, which make them all completely useless......probably 20 of them, and I know there are many more across the globe that suffered the same fate......this may be an option to fix these no longer supported bits of gear.
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this may be an option to fix these no longer supported bits of gear.
I wonder why no one made replacement LCD displays for all that agilent gear with VFD displays yet, currently you have to pay like $70+ to get one from remaining old stock.
People would be ok to pay like up to $30 for this, where display would cost about $3 to maufacture + $2 some DC/DC converter for backlight.
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Hi.
I've designed a custom lcd, recently, too. It uses the HT1621 controller, I've created all the libraries to control it from a microcontroller, but apparently every time I load the data it remember only the last common enabled. Later it fades away.
Is there any setup in the controller that I'm missing?
Any idea?
Thanks in advance.