Author Topic: How to Drive VFD tube with MCU?  (Read 16412 times)

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Offline sdttn

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How to Drive VFD tube with MCU?
« on: June 30, 2011, 05:36:40 pm »
Hi,
I need to learn how to connect the PT6311 (VFD Driver IC with serial interface)

I did not know which serial standards in this IC.  :-\
Which comand I need to use in Pic Basic Pro.
I am planing to use 16f628
Thanks.
« Last Edit: July 09, 2011, 05:12:22 pm by sdttn »
 

Alex

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Re: PIC serial interface (PBP)
« Reply #1 on: June 30, 2011, 09:52:28 pm »
Before we do anything, you linked a VFD on the chatbox.

http://cgi.ebay.com/Vacuum-Fluorescent-Display-8-digit-VFD-clock-nixie-tube-/270747473445?pt=Vintage_Electronics_R2&hash=item3f09ce9625

You are not seriously thinking of buying this at $400  :o Previous 2 were sold for 2 orders of magnitude less, clearly the seller messed up.

First find the VFD you want, and its bloody datasheet. I am tired of ebay sellers not providing a datasheet unless you buy the product. What are they thinking?!  >:(
 

Offline sdttn

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Re: PIC serial interface (PBP)
« Reply #2 on: June 30, 2011, 10:05:50 pm »
I have already had just two of them before. 
There is no fancy thing about the VFD.

The datasheet on attachment.
« Last Edit: June 30, 2011, 10:11:09 pm by sdttn »
 

Alex

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Re: PIC serial interface (PBP)
« Reply #3 on: June 30, 2011, 10:17:44 pm »
Most excellent!

Now, are you forced to use the PT6311 driver?  As this is a small multiplexed display it will be easy to use a (40 pin?) MCU with a handful of transistors to drive the display. You can also use specialised shift register latches from eg Maxim, designed to drive VFDs.
 

Offline sdttn

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Re: PIC serial interface (PBP)
« Reply #4 on: June 30, 2011, 10:43:04 pm »
No,
I prefer PT6311 because of the serial interface it use 3 pin.
Can you say me the maxim ICs?
Thanks for your help.
 

Alex

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Re: PIC serial interface (PBP)
« Reply #5 on: June 30, 2011, 10:56:55 pm »
Ok. Regarding the Maxim drivers, you can have 8 control grids and 15 segments per digit. Thats 23 total.

You can use two MAX6920s that can drive 24 anodes (12 each), or a single bigger IC from the same family like the MAX6922/MAX6932/MAX6933/MAX6934

http://datasheets.maxim-ic.com/en/ds/MAX6922-MAX6934.pdf

They are using an SPI interface, but you dont need to write a low-level driver for it using commands, just send out the data you want to display. You can also sample them for free, I have 9x 6934s in front of me for a clock. Some of them allow you to apply a positive bias to the grid with respect to the anodes.

There are other obscure drivers around...if you dont like the Maxim ones.
 

Offline sdttn

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Re: PIC serial interface (PBP)
« Reply #6 on: July 01, 2011, 12:02:09 am »
I do not know if maxim send to my side sample.

I found this

 

Alex

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Re: PIC serial interface (PBP)
« Reply #7 on: July 01, 2011, 12:55:38 am »
Yeah, thats the idea. Which ICs are these? These seem to share voltage supply for the control logic and the drivers.
 

Offline sdttn

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Re: PIC serial interface (PBP)
« Reply #8 on: July 01, 2011, 01:12:20 am »
They are HCF4094Bs.

But I did not understand how to write the program.
The VFD tube must be multible drive. How the shift register ICs working with multiple VFD tube?

http://spritesmods.com/?art=vfdcontroller&page=2
« Last Edit: July 01, 2011, 01:14:56 am by sdttn »
 

Alex

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Re: PIC serial interface (PBP)
« Reply #9 on: July 01, 2011, 12:14:25 pm »
Ok.

You need to understand the operation of a shift register and possibly D-type flip flops first. Look online, loads of info.

The MCU sends out a 24 bit wide bitstream to the data line of the first register here. This is shifted inside the register chain with the CLK line signal. When the bitstream has finished being shifted in the registers the Strobe signal is asserted and the bit stream is transfered to the output drivers. The first 11 bits (in this application) will appear at the end, and they will drive the control grids. The remaining 13 bits appear on the left and drive the segments.

To display different numbers at different positions on the display, you need to use persistence of vision (PoV). First prepare the bit stream to address the first digit, then shift it all out and replace it with the bitstream for the next etc. This is inefficient but it will work.

Does this make any sense?
 

Offline sdttn

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Re: PIC serial interface (PBP)
« Reply #10 on: July 04, 2011, 09:48:38 pm »
Yes, but still I am interesting in PT6311
I found more readable datasheet of PT6311. (Added to attachment)


I did not understand ram addreses. Can you tell me what does the table (page 8 ) mean?



« Last Edit: July 04, 2011, 10:46:22 pm by sdttn »
 

Alex

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Re: PIC serial interface (PBP)
« Reply #11 on: July 04, 2011, 09:56:28 pm »
Why so interested in this chip? It feels like a 'Chinese ASIC' or one of those badly documented ICs from Futaba...

That table is the display RAM. Anything that you write in the is displayed on the screen, constantly I believe with the controller taking care of the multiplexing.
 

Offline sdttn

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Re: PIC serial interface (PBP)
« Reply #12 on: July 04, 2011, 10:58:49 pm »
But, the IC have timer I think the timer taking care of multiplex driving.

I found an other IC this chip from NEC. It is UPD16312. (Datasheet attached)

It is actually same as PT6311.
 

Alex

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Re: PIC serial interface (PBP)
« Reply #13 on: July 04, 2011, 11:09:56 pm »
It's very easy to do with the main mcu and a timer interrupt. Anyway, it appears it is made by more than one manufacturers.
 

Offline sdttn

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Re: PIC serial interface (PBP)
« Reply #14 on: July 05, 2011, 09:08:55 pm »
I found C code for the PT6311.
But I can write just in BASIC lang.

The code files are attached.
 

Alex

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Re: PIC serial interface (PBP)
« Reply #15 on: July 05, 2011, 09:17:41 pm »
BASIC is great, but it is...basic. You should learn C that is standard in the industry. Once you know one programming language the others are easier.
 

Offline sdttn

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Re: PIC serial interface (PBP)
« Reply #16 on: July 09, 2011, 04:30:49 pm »
Yes I will learn C.

I found UDN1628. It is VFD driver IC.

What do you think?



The datasheet atthached.

Thanks Alex.
 

Alex

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Re: PIC serial interface (PBP)
« Reply #17 on: July 09, 2011, 04:42:38 pm »
Yes, these will work fine. Have you found a supplier for these?
 

Offline sdttn

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Re: PIC serial interface (PBP)
« Reply #18 on: July 09, 2011, 05:01:23 pm »
Yes, these will work fine. Have you found a supplier for these?

Yes I found local supplier for the ICs.
It is 1.5 USD.

BTW actual photo of this VFD tube.




I made a video:

 

Alex

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Re: PIC serial interface (PBP)
« Reply #19 on: July 09, 2011, 05:04:38 pm »
Reminds me of Grandstand Astrowars  ;) Alright, time to buy a controller now.
 

Offline sdttn

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Re: How to Drive VFD tube with MCU?
« Reply #20 on: July 09, 2011, 05:19:04 pm »
The game which looks like Glaxian :)

I am planing to use 16F877. I have already one.

Actually I want to make a preamp with PGA2311 (Digital Stepped Attenuator) it use serial interface but it is so simple as I can understand.

VFD module PCB.



 

Offline sdttn

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Re: How to Drive VFD tube with MCU?
« Reply #21 on: July 13, 2011, 06:23:42 pm »
ICs are came up.
I performed a test.

I hooked the one of IC out pins to grids and one of other to segment up.


 


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