Alternative Serial Displays
eagletalontim
Posts: 1,399
Hello all once again! I have a project that is currently using the 16 X 2 back lit serial display from Parallax. I plan to market my completed project but I would like to get the cost down as much as possible. Right now, I am hoping to find a serial display that will work with the prop that is not $30 a piece (no offense to Parallax!) Since the serial display only takes up 1 pin, I would like to stay with that if at all possible. Does anyone have some recommendations of where I could find cheaper displays?
Comments
http://www.phanderson.com/lcd106/lcd107.html
The serial ones do seem to be more expensive than the parallel ones, but if you only have one pin left... (hands up who wants more pins on the propeller?!)
... I put my hand up as well
http://search.digikey.com/us/en/products/M0216SD-162SDAR2-1/M0216SD-162SDAR2-1-ND/1739768
I am hoping for a black background with different color options for the characters. One color per display though... I don't know what they are called if they are even called anything special.
Or you could use 3 pins and use HC595 chips.
Or 3 pins and drive a TV screen ("car reversing" displays are under $30 and propeller objects work out of the box).
And I think Cluso did a TV driver that had two colors and one pin. Fine if you just want to display text.
What is the display for?
I will also need some sort of enclosure with the display to allow customers to mount the display anywhere they want in their vehicle away from the "main brain".
I just found this, but I really have no idea what I am looking at when it comes to communication between the chip and the display. http://www.seeedstudio.com/depot/lcd-204-characters-white-back-light-p-350.html?cPath=163_164
A 20 X 4 for $16.50.... that is really cheap.. question is, would it work with the Prop and if so, what driver would I need?
Tim,
Check out this Futurlec link. www.futurlec.com/LCDDisp.shtml
While these are all parallel displays, there are many objects for devices based on this chip including a three-wire Object I put up. Also, someone also posted they could go a bit further and do it with one wire. If you can get by with 16*4, they get a bit cheaper. I don't think green is unprofessional, even fluke used green back lighting in their Kiethley dose measuring systems. If you are looking at cool, consider blue back light.
Good luck,
Frank
Below is a little terminal I wrote for a 20x4 display. It outputs via a latch but only uses 6 pins, so you could easily change the PUB LCDOutput so it outputs directly from 6 propeller pins. Just a few lines of spin code to change.
These displays are all very similar - they can run in "4 bit" mode so you split a byte into two and send it out in two parts. Then there are two control pins. So 6 pins in total.
'' parallel 20x4 lcd driver for the DracBlade including a 'Terminal' that scrolls properly, backspace etc CON _clkmode = xtal1 + pll16x ' use crystal x 16 _xinfreq = 5_000_000 LatchDirection =%00000000_00000000_00001111_11111111 ' 138 active, gate active and 8 data lines active MaskLowByte = %00000000_00000000_00000000_11111111 ' used in lots of routines to & mask off low byte LCDLatch = %00000000_00000000_00001011_00000000 ' LCD latch is xxxx101x and gate high xxxxxxx1 EnableBit = %00000000_00000000_00000000_00000010 ' Enable pin 6 on LCD displays OBJ delay : "timing" VAR long Char ' Character To Send To LCD long Inst ' Instuction To Send To LCD long Column ' column counter for line 4 ' don't use byte, causes all sorts of overrun errors long LineNumber ' line number 1,2,3,4 long LCDChar ' character to send to LCD 0-$FF long LCDByte ' byte to latch out to LCD display byte Display[79] ' buffer for display 20x4 ' put this last as bizarre overwriting going on PUB Start | n Init_Lcd Column:=0 ' start at zero repeat n from 0 to 79 ' fill the display memory with spaces Display[n]:=" " 'fill with spaces Redraw { repeat 25 ' test code for running standalone out(65) out(10) out(66) out(13) } PUB str(stringptr) '' Print a zero-terminated string repeat strsize(stringptr) out(byte[stringptr++]) PUB dec(value) | i '' Print a decimal number if value < 0 -value out("-") i := 1_000_000_000 repeat 10 if value => i out(value / i + "0") value //= i result~~ elseif result or i == 1 out("0") i /= 10 PUB hex(value, digits) '' Print a hexadecimal number value <<= (8 - digits) << 2 repeat digits out(lookupz((value <-= 4) & $F : "0".."9", "A".."F")) PUB bin(value, digits) '' Print a binary number value <<= 32 - digits repeat digits out((value <-= 1) & 1 + "0") PUB out(c) | i,j ' Output a character, ignores most <32 and all >126 ' possibly add a 'turn on display' and 'turn off display' with selected ascii characters ?? esc seq i:=c ' need a local working variable as an if statement seems to corrupt subsequent working variables! j:=Column ' and need a local version of column otherwise corrupts this too if c==10 ' Linefeed Newline Column:=0 ' reset column counter j:=21 ' ensures code below doesn't run if j<20 ' this LCD driver code is slow so better to not print anything after line 20 and wait for CRLF ' if j > 19 ' is it off the end of the display? (old display wrapped around) ' Column:=0 ' reset to beginning ' Newline if c==08 ' Backspace Backspace ' if c==13 ' do nothing as LF includes CR as part of the code if i >= 31 ' and statements don't work in if lines?! if i<=126 ' send the ascii character char := c ' get the character Send_Text ' send it out Display[Column+60]:=c ' store the character in the last column Column:=Column+1 ' add 1 to column if j==19 CursorOff PUB CursorOn Inst:=13 ' turn on the cursor Send_Inst PUB CursorOff Inst:=12 ' cursor off Send_Inst ' send the instruction PRI Init_Lcd LCDLow ' set the 6 LCD lines low delay.pause1ms(200) ' short delay for LCD bootup 200ms LCDByte:=%00001100 ' send out 0011 already shifted to xxnnnnxx PulsOut LCDByte:=%00001100 ' send out 0011 already shifted to xxnnnnxx PulsOut LCDByte:=%00001100 ' send out 0011 already shifted to xxnnnnxx PulsOut LCDByte:=%00001000 ' send out 0010 already shifted to xxnnnnxx PulsOut LCDByte:=%00001000 ' send out 0010 already shifted to xxnnnnxx PulsOut LCDByte:=%00100000 ' send out 1000 already shifted to xxnnnnxx PulsOut Inst:=14 ' cursor on Send_Inst Inst:=1 ' cls Send_Inst Inst:=13 ' flashing cursor Send_Inst Inst:=128 ' to position 1 Send_Inst pri Send_Inst ' send instruction in Inst RSLow ' not actually needed see below but makes code more logical LCDByte:=Inst ' get high nibble LCDByte:=LCDByte>>2 ' shift right two bits so xxnnnn00 LCDByte:=LCDByte & %00111100 ' mask the nibble and sets RS low as well (bit0) Pulsout ' send it out LCDByte:=Inst ' get low nibble LCDByte:=LCDByte<<2 ' shift left two bits so xxnnnn00 LCDByte:=LCDByte & %00111100 ' mask the nibble and sets RS low as well (bit0) Pulsout ' send it out RSHigh ' back to text mode pri Send_Text ' pass Char = a byte 'RS always high = bit 0, bits are xxnnnnER where nnnn is the nibble, E=enable and R=RS LCDByte:=Char LCDByte:=LCDByte>>2 ' shift right two bits so xxnnnn00 LCDByte:=LCDByte & %00111100 ' mask off just the nibble LCDByte:=LCDByte | %00000001 ' keep RS high Pulsout ' send it out LCDByte:=Char ' get low nibble LCDByte:=LCDByte<<2 ' shift left two bits so xxnnnn00 LCDByte:=LCDByte | %00000001 ' keep RS high Pulsout pub Next_Line Inst := %11000000 ' Move Cursor To Line 2 Send_Inst PRI ToggleGate OUTA[8]:=0 ' set gate pin low OUTA[8]:=1 ' and high again - may need a delay in PASM PRI EnableLatchPins DIRA:=LatchDirection ' 138 active, gate active and 8 data lines active PRI Tristate ' tristate all pins DIRA:=%00000000_00000000_00000000_00000000 PUB LCDOutput | n ' sends byte LCDByte to latch EnableLatchPins ' turn on the pins needed to talk to the latches n:=LCDByte ' byte value to send out n:=(n & MaskLowByte) ' 2 AND mask the low byte n:=(n | LCDLatch ) ' 3 OR with the LCD address 138 OUTA:=n ' 4 send it out ToggleGate ' 5 and latch it tristate ' back to tristate on all pins PUB LCDLow ' sets all LCD pins low for startup LCDByte:=0 LCDOutput PUB PulsOut ' pulse the enable pin 6 high then low - uses LCDByte and returns it unchanged LCDByte:=(LCDByte | %00000010) ' logical OR to set just this bit high LCDOutput ' send it out ' delay.pause1ms(1) ' short pause not needed as spin very fast LCDByte:=(LCDByte & %11111101) ' logical AND set just this bit low LCDOutput ' send it out ' delay.pause1ms(1) ' delay for LCD to process it PUB RSHigh ' set RS pin 4 high - uses LCDByte and returns it unchanged LCDByte:=(LCDByte | %00000001) ' logical OR to set just this bit high LCDOutput PUB RSLow ' set RS pin 4 low - uses LCDByte and returns it unchanged LCDByte:=(LCDByte & %11111110) ' logical AND set just this bit low LCDOutput PUB Backspace | i,j ' backspace is a special case - need to subtract 1 off the column, make the last character a space ' and redraw the screen and print out column number of characters on last line ' only really works on line 4 but most of the time the display is on line 4 anyway j:=Column ' the last character added 1 to column so start with one less if j>1 ' not reliable at 1 Display[Column+60-1]:=32 ' was one past the character Column:=Column-1 ' subtract 1 Redraw repeat i from 0 to j-2 Char:=Display[60+i] ' print out the last row with one less character Send_Text PUB Redraw ' redraw the entire screen Inst:=128 ' line 1 Send_Inst LineNumber:=1 ' print line 1 Printline Inst:=192 ' line 2 Send_Inst LineNumber:=2 ' print line 2 Printline Inst:=148 ' line 3 Send_Inst LineNumber:=3 ' print line 3 Printline Inst:=212 ' line 4 Send_Inst LineNumber:=4 ' print line 4 Printline Inst:=212 ' cursor to beginning of line 4 Send_Inst CursorOn PUB PrintLine | n ' Prints the line in LineNumber 1 to 4 n:=(LineNumber-1)*20 ' convert to pointer for the array 0-79 repeat 20 ' do this 20 times Char:=Display[n] ' get the character from the array Send_Text ' send it out n:=n+1 ' increment counter PUB Newline | i ' move the lines all up one, clear line 4, move cursor to position 1 of line 4 repeat i from 0 to 59 ' move up to next line Display[i]:=Display[i+20] repeat i from 60 to 79 Display[i]:=32 ' space Column:=0 ' column counter to zero Redraw ' redraw the screenThis is basically what I am hoping to find that would hopefully be a direct replacement for the parallax 16 X 2 display.
https://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2137764_-1
As of right now, I have 9 more pins open on the Prop. 8 of them are driving a 7 segment display which takes up quite a bit already. Since I would like to allow users to plug in their own addons to the product, I need to have at least 5 open pins for them to have access to. I am still in development stages and I will probably need 3 or 4 more pins to complete a few more features.
http://www.wulfden.org/TheShoppe/k107/index.shtml
Re serial vs parallel, you only need 6 pins to drive these displays. So that can be 6 propeller pins. Or you can share some pins with something else (eg your 7 segment display - blank the display briefly while you output data), or use a 74HC595 which reduces the pin count to 3 pins (45c at jameco).
In serial mode it is using 4 pins and looks like a standard SPI interface. CS would always be enabled so maybe 3 pins? Maybe even 2 pins because you could ignore data coming back from the display.
I saw this thread earlier and I was just about to suggest the same thing.
Daisy chain two 595s together and drive both the 7-segment and LCD with 3 pins. If you don't your competitor will likely do it.
Has anyone driven a LCD with a shift register? I wouldn't think it would be very difficult.
Tim, I think you ought to give eBay another try. Just buy a few low cost items from a seller to make sure they're legitimite and then order larger batches from the same seller once you're comfortable with the seller.
Here's a $3 LCD. The $3 includes shipping. An awfully safe bet. (I've personally purchased many items from this seller (including this LCD).)
I think the reason you don't find inexpensive serial LCDs is because there made for hobbiests. People like us who are willing to pay extra for the simplicity of a serial interface to use in our one-off creations. I really doubt there are serial LCDs being used as components in high volume products.
Link to Microtips .pdf on VLCD vs. VFD
Link to www.newhavendisplay.com
This on : http://www.newhavendisplay.com/index.php?main_page=product_info&cPath=253&products_id=2391 looks pretty nice, but, question is, would I be able to use the LCDupdate code Dr_Acula posted with this display? I also need an enclosure to put just the display in. Are these made to fit in already made enclosures readily available on the web?
I suppose a car has plenty of other light sources to spoil ones night vision. I'm just wondering if the color of light used with the display should be a concern or not?
Come to think of it, I think I've seen a lot of blueish car displays in the past so it probably doesn't matter.
I have one of those as well. I wrote an OBEX driver that will work with the 16x2 or 20x4 http://obex.parallax.com/objects/798/
I have never come across enclosures made for LCDs...
"There are many solutions and I've gone for one that uses the lower 12 propeller pins through latches to give 64 digital I/O. Latch chips are under $1."
Would you be able to share the schematic and idea for your 12 to 64 bit io interface.
Thnaks
Rich
Duane,
The object "3 I/O Pin Hiatchi Compatible LCD Driver" is based on a PowerTip PC2400LRF (just another hitatchi compatible clone LCD display) and one 74xx164 shift register.
As to going with ebay, that is fine as far as the initial development or for a personal one off. Tim however will be looking at production runs (even if not many to start). He will need reliable sources of current parts to support production and eventually repairs. eBay is loaded with pulls, overstock, and closeouts that may not be available reliably for future production.
Frank
Sure. I don't have access to schematics on this computer, but essentially take 8 propeller pins and call this a bidirectional bus and connect to latches for outputs or 244 chips for inputs. Each of those chips has a 'chip enable' pin that enables the pin when it goes low. Use 4 propeller pins to drive a 138. Three pins select which of 8 outputs goes low. The fourth pin enables the 138, so you can make all pins high and disable all outputs.
If you are ok about 64-8 = 56 i/o pins, you could do this with 11 pins instead of 12.
There are many options for driving displays. To me, just using 6 pins on the propeller seems simplest.
There are many sources for 20x4 LCD displays (I like the white on blue ones) so if one supplier can't get them, many others can.
http://www.mouser.com/electronicassembly/ (2nd item on the list)
I have two of them, but haven't actually tried them yet.
Jason
http://www.bgmicro.com/ncrfutaba4x20vacuumfluorescentdisplay.aspx
If there are none, what other displays are there that have an enclosure it will fit right into? This is for an automotive application so it has to be durable.
The idea that I have is to have a main brain that does all the processing and computing for my product. A user can connect an external LCD display to place anywhere they want in their vehicle. There is also an external 7 segment display that will be connected to the main brain that will be a quick reference for the user to look at when needing to see what gear they are in. I may be able to eliminate the 7 segment display and open up 8 pins on the prop to allow for a more powerful display if needed. Cost is the biggest thing at the moment though!
You would be doing yourself a tremendous service by making the attempt. So many newbies want to find ready-made solutions for every problem and they just do not exist. The good news is that programming is programming, and if someone's done it on an Arduino you can generally port it to the Propeller without much pain -- I do it all the time.