Is this the simple LCD I want to use?

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manuka

Senior Member
What are you thinking of doing? Although most 16x2 displays follow Hitachi style addressing, all sorts of boring issues may arise - serial,baud rate,supply voltage,current drain,backlit,contrast,word wrapping, true descenders,panel mounting cutout, package size etc. Extra circuitry may hence well be needed for 2400 bps PICAXE connecting with cheapie LCDs. I've had good mileage using terminal programs on older PDAs/Organisers in fact- their larger screen allows better information display as well.

Thought: Consider beeping tones/flashing or coloured LED outputs? These may be quite sufficient for status & alerts, & of course have cross cultural & age benefits - even animals can respond to specific sounds. Few preschoolers/"lost my reading glasses" pensioners/foreign language users may be able to read your LCD text anyway, yet most would quickly respond to flashing red lights or urgent beeps. Stan
 

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W

westaust55

Moderator
RogerTango said:
http://www.sparkfun.com/commerce/product_info.php?products_id=812

Reasonable priced, serial enabled LCD. AFAIK, this is what I want to use with my projects. I want to be able to use as FEW IO pins as needed.

How about this one?
http://www.sparkfun.com/commerce/product_info.php?products_id=791
I supposed it CAN be used, but will tie up all my IO pins to drive it.

Thanks,
Andrew
Click to expand...

From the second Sparkfun link you gave:
You will need ~11 general I/O pins to interface to this LCD screen.

You need an LCD with TTL level serial interface (not RS232) or an i2c interface.
There require 1 IO or 2 IO respectively. Some of the smaller PICAXE do not have i2c comms implimented.

To get the serial or i2c comms interface you need a separate board to the LCD module.

EDIT:
Manuka got in just before me but also had another valid point - baud rate.
The ideal is to have a 2400 and or 4800 Baud serial interface.
Some devices have 9600 baud but this is not supportred by the PICAXE when operating at 4MHz.
 
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RogerTango

Senior Member
Good information so far, but the question has not been fully answered yet. Some of the projects I want to work on would NEED an LCD display. Temp sensors for one, where you would want to see the actual temp, or the high and low temp history.. Or like I discussed elsewhere, a battery monitor, where I would want to see the actual voltage and the last voltage under load. It would be a bit of a pain to encode 12.50 volts into some flashing LED schema! HA HA!

Thanks,
Andrew
 
hippy

hippy

Ex-Staff (retired)
RogerTango said:
http://www.sparkfun.com/commerce/product_info.php?products_id=791
I supposed it CAN be used, but will tie up all my IO pins to drive it.
Click to expand...
Most HD44780 ( including that I would guess ) can work in 'nibble mode'; that needs just four data plus two control lines so not too bad I/O wise.

http://www.hippy.freeserve.co.uk/picaxelc.htm

You can also build a serial to parallel interface which can drive the LCD and use even less I/O lines but that does increase the hardware. You could use a 14M/20M as a serial to LCD interface and Rev-Ed sell FRM010, a PICmicro which does that as well.
 
D

Dippy

Moderator
"Good information so far, but the question has not been fully answered yet."

- well, what precisely is the question?

Will they work? Which ones will work?

People here have got most types of LCDs to work ; ranging from good quality ones from reputable suppliers to the cheapest tosh from unknown Ebay vendors.

The serial type LCD will require the fewest data lines (or wires).
They should be the easiest to get going and use the least code on your PICAXE - as their on-board (usu PIC) does the hard work for you.

The parallel type which have a minimum config of 4 data plus a few control obviously require more legs on your PICAXE but will be cheaper.

So, bottom line: price vs convenience? That's your decision. If I were just starting I'd spend the extra and get the serial type or an LCD+firmware board. Once I'd got my first project running then I would consider a cheaper parallel LCD, which is harder to implement unless you copy all the necessary code from here :)

But for me to 'recommend' an LCD and imply that you will get it working in 5 minutes may be a little silly.

My un-humble and totally biased advice:-
For your first foray (where you want something that is definitely working when you buy it) then spend a few extra pennies and get it from a reputable supplier.
Spend even more extra pennies and go for serial type unless you are confident/competent with coding.

(You may be lucky with some cheap Ebay sourced guff, but if it's duff and you are unsure about your code, then how will you know? And will you really want to spend 3 weeks posting on this Forum before you find out? All to save a fiver....?)
 
W

westaust55

Moderator
RogerTango said:
Good information so far, but the question has not been fully answered yet. Some of the projects I want to work on would NEED an LCD display. Temp sensors for one, where you would want to see the actual temp, or the high and low temp history.. Or like I discussed elsewhere, a battery monitor, where I would want to see the actual voltage and the last voltage under load. It would be a bit of a pain to encode 12.50 volts into some flashing LED schema! HA HA!

Thanks,
Andrew
Click to expand...
Ah, not necessarily always the case to have an LCD.
I have a bar graph of LED's that I have used for a graphical indication of the temperature. If the range is not too great 1degree per LED is sufficient for some application. May want better resolution for that brewery operation :)

Many commercial battery monitors only have a series of LED's to indicate the voltage in 1 or 2 volt steps.
 
W

westaust55

Moderator
RogerTango said:
Good information so far, but the question has not been fully answered yet.

Thanks,
Andrew
Click to expand...
In my post (see post 6) I stated:
You need an LCD with TTL level serial interface (not RS232) or an i2c interface.
These require 1 IO or 2 IO respectively. Some of the smaller PICAXE do not have i2c comms implimented.

:
:
:

The ideal is to have a 2400 and or 4800 Baud serial interface.
Some devices have 9600 baud but this is not supported by the PICAXE when operating at 4MHz.

and
Click to expand...
The first Sparkfun link you gave states:
The SerLCD backpack takes care of all the HD44780 commands allowing seamless integration with any micro that can communicate at 9600bps TTL serial
Click to expand...

So it is TTL interface as required

But . . . .it is not 2400 or 4800 Baud and therefore cannot be used with a PICAXE at 4MHz. Would work with a PICAXE operating at 8MHz.

Have a look at PICAXE manual 2 page 151 for the SEROUT command for details on applicable speeds.


So what is left to answer ? :confused:
 
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Dippy

Moderator
Good point re: baud rate and TTL levels and you should check whichever PICAXE you intend to use.

(And don't forget the extra space for a serial i/f board)

That first Sparkfun link looks good initially , but as WA points out be aware of the baud rate.
The Data sheet amused me. It says other bauds can be set, but implies you first have to connect it to something at 9600 to be able to send a command to change the baud. Para 3.4.
Dear oh dear. (To be taken back if I misread :))
Even I could write a better firmware than that.
 
B

BeanieBots

Moderator
What about the good old AXE033 from Rev-Ed?
Serial or I2C comms. (one or two I/O pins only).
Fully supported HERE.
2 X 16 characters.
Very cheap. Very reliable. Only about 4mA.
No backlight but VERY readable even in poor lighting.
 
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RogerTango

Senior Member
Okay, I read properly now. Someone remind me to not post when Im overly tired! HA HA!

Thanks for everyone's help!!

Andrew
 
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