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Problem with vfd display in 4bit mode


QBAS
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Hi

I hope it is right place for this topic :)

I just programmed pic18f4685 (thanks Wilba http://www.midibox.org/forum/index.php?topic=8328.msg58220#msg58220).

I have done all changes - 4bit connection for LCD, CAN bus with diodes-

uploaded new midibox_sid_v1_74685 code - but since I go to 4bit, my VFD http://www.bipom.com/documents/peripherals/vfd202.pdf

not working OK. It go to "pause" after second. Sometimes it show nothing, sometimes only small part of screen.

In 8bit everything was Ok, but I don`t know why in 4bit there are problem - since on datasheet is also 4bit mode.

Someone has the same problem?

I would like to say that on another LCD 2x40 everything work OK in this mode, but I prepare CS just for this smaller VFD!

Maybe it is the same problem like has Wilba on his PLED in 4bit mode?

Can someone help me? Any suggestion?

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more than likely the problem is 4-bit mode... my tests show that after each command it sends, it gets back a status byte, and sometimes the two 4-bit nibbles are in the wrong order, so depending on the cursor address, MIOS thinks it stays busy until a timeout is reached.

I've written a custom LCD driver that uses 8-bit mode by using two pins on port E to replace the two pins being used by the CAN... you'll need to add wires and ensure D0 and D1 are still connected to port B pins, and D2 and D3 connect to port E1 and E2.

http://www.midibox.org/dokuwiki/doku.php?id=pic18f4685_8bit_lcd_driver

This solves the problem with my 4x20 PLED and have not had a problem since.

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Fast and precision, in point.

Thank you Wilba. You known that I asked you for this driver, but not directly.

When I see (one minute after I post my problem) that you read this, I get relax.

OK- now I will check, I hope no more "questions" will be - only "thanks"....

.... after 3 hours tryings, of course with removed gound on D0-D3, and done all needed connections. Unfortunatelly the effect is the same.

I will try to change driver, if you give me a link for datasheet of your pled Wilba then I will compare differences - maybe it "give me some inspiration" - like said T.K oneday.

My vfd sometimes work for 3 seconds intensive with changing patches fast for egz., sometimes initialize failure.... I feel that it is possible to get it work, but I can`t find where is problem.

Also all time regular LCD work good.

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WOOOOHAAAA!!! ;D ;D ;D :D

It work!!!

Since it was my first time (and very interesting) with custom LCD driver,

I forgot to add in USER_Init changing of #7 LCD  -  user driver.

Now - witchout any changes of orginal Wilba`s driver - everything is showing good.

I`m happy. Thank you!!!

Time to check what is a time response of other SID`s by CAN. 8)

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