Driving a 2x16 LCD with only One Pin and 74HC595

1 Attachment(s)

Hello,

with the idea from this WebSide http://www.romanblack.com/shift1.htm, using the Darrel Taylor LCD_AnyPin.pbp + HighJack as a template and the willing to drive the LCD with only one Pin and to use the LCDOUT Command with all features, i wrote a routine for the 74HC595 controlling.

Attachment 7206

and here is the Code:

Code:

@ DEVICE pic16F628A, intOSC_osc_noclkout, WDT_OFF, PWRT_OFF, BOD_OFF, MCLR_OFF define osc 8 INTCON = 0 PortA = 0 PortB = 0 TRISA = 0 ' CATODES TO PORTA TRISB = 0 ' ANODES TO PORTB CMCON = 7 Serial_Pin var PortA.3 B0 var byte B1 VAR Byte B2 VAR Byte B3 VAR Byte B4 var Byte B5 VAR Byte B6 VAR Byte B7 VAR Byte B0 = 0 B1 = 255 ;----[ Change these to match your LCD ]--------------------------------------- INCLUDE "One_Wire_74HC595.pbp" ; *** Include MUST be AFTER LCD Pin assignments * ;----[ Your Main program starts here ]---------------------------------------- LCDOUT $FE, 1 LCDOUT $FE, 1, IHex 255 Pause 2000 Start: Repeat B0 = B0 + 1 B1 = B1 - 1 B2 = B0 DIG 2 B3 = B0 DIG 1 B4 = B0 Dig 0 B5 = B1 DIG 2 B6 = B1 DIG 1 B7 = B1 Dig 0 LCDOUT $FE,$80,"Counter = ",#B2,#B3,#B4 LCDOUT $FE,$C0,"Counter = ",#B5,#B6,#B7 Pause 1000 Until B0 > 254 OR B1 < 1 SWAP B0, B1 goto Start END

Code:

A var byte B var byte C var byte D var bit E VAR byte INCLUDE "VirtualPort.bas" LCD_DATAUS CON 2000 LCD_COMMANDUS CON 50 'PAUSE 100 : LCDOUT $FE,1 : PAUSE 100 ; Initialize LCD Goto Over_One_Wire_74HC595 ;===============( DO NOT Change anything below this line )==================== ASM ; Make sure HighJack has been installed in PBP's .LIB file ifndef LCDOUT_HIGHJACKED error "HighJacked-LCDOUT Not found in PBPPIC??.LIB" endif ENDASM DEFINE HJ_LCDOUT _LCDsend ; Redirect PBP's LCDOUT to LCDsend: Subroutine ;----[Send a byte to the Virtual LCD PORT]------------(DO NOT Change)--------- TempChar var byte Char VAR Byte LCD_Initialized VAR FLAGS.1 RSS VAR FLAGS.0 ; LCD RS State ;----[ This routine is called once for every character sent by LCDOUT ]------- LCDsend: @ MOVE?AB _TempChar ; Get char sent by LCDOUT, in WREG if !LCD_Initialized then LCD_Init ; Make sure LCD was Initialized LCDAfterInit: if TempChar = $FE then RSS=0 : goto LCDsendDone ; next char is Command Char = TempChar LCDsendCOM: Gosub Toggle_Nibble IF RSS = 0 then ; Is a Command IF Char = 1 then CommandDelay ; Long delay for Clear Screen IF Char = 2 then CommandDelay ; Long delay for Home @ DelayUS _LCD_DATAUS ; Short delay for everything else goto DelayDone else @ DelayUS _LCD_DATAUS ; Short delay for Data goto DelayDone endif CommandDelay: @ DelayUS _LCD_COMMANDUS DelayDone: if LCD_Initialized then RSS = 1 ; Set RS to Data next time LCDsendDone: return ;----[Initialize the LCD]-------------------(DO NOT Change)------------------- LCD_Init: A = 2 Char = $33 : gosub LCDsendCOM : @ DelayUS 5000 gosub LCDsendCOM : @ DelayUS 100 gosub LCDsendCOM : @ DelayUS 100 Char = $22 : gosub LCDsendCOM ; Start 4-bit mode A = 5 Char = $28 : gosub LCDsendCOM ; Function Set, 4-bit, 2-line, 5x7 Char = $0C : gosub LCDsendCOM ; Display ON Char = $06 : gosub LCDsendCOM ; Entry Mode LCD_Initialized = 1 ; LCD has been Initialized goto LCDAfterInit Toggle_Nibble: For C = 0 to A SELECT CASE c CASE 0 B = Char & %11110000 ' Upper 4 Bits If RSS = 1 Then B = B | %00000100 ' Set RS Bit Endif CASE 1, 4 B = B | %00001000 ' Set Enable Bit CASE 2, 5 B = B ^ %00001000 ' Enable Toggel Case 3 B = Char * 16 ' Lower 4 Bits Shift If RSS = 1 Then B = B | %00000100 ' Set RS Bit Endif END SELECT '******************************Shift_74HC595*********************************** E = 7 Repeat D = B >> E E = E - 1 SELECT CASE D CASE 1 Serial_Pin = 0 @ nop ' min 1 µs for 1 Serial_Pin = 1 Pauseus 15 ' min 15 µs Case 0 Serial_Pin = 0 Pauseus 15 ' min 15 µs for 0 Serial_Pin = 1 Pauseus 30 ' min 30 µs danach END SELECT Until E = 0 'Latch Serial_Pin = 0 Pauseus 200 ' min 200 µs for Latch Serial_Pin = 1 Pauseus 300 ' min 300 µs Next Return Over_One_Wire_74HC595:

As long as Strings will be send, all runs pretty good
Example:
LCDOUT $FE, 1, "Hello"

But I can do what I want, everytime I want to use the HEX, BIN, DEC, REP or STR commands i get Errors in displaying the correct Data.

Example:
LCDOUT, $FE, 1 IHex 255

I get F0 as answer and not $FF
Without I the answer is $220

What I also found out is, when I wrote a simple loop that show me the Hex Characters from 1 to 20....
Till 16 all is Displayed correct. After 16 till 20, 10 is displaying.

I hope somebody can help me.

Thanks

P.S. Sorry for my Bad English

Re: Driving a 2x16 LCD with only One Pin and 74HC595

Change all of your PAUSEUS's to @ DelayUS xxx

PAUSEUS will change PBP's system variables that are already in use creating ASCII characters from a value using DEC, BIN, HEX etc.
@ DelayUS does not use the system vars.

Re: Driving a 2x16 LCD with only One Pin and 74HC595

Hi Darrel,

First, Thanks for your Help.

I replace all, but the situation is the same.

1 Attachment(s)

Re: Driving a 2x16 LCD with only One Pin and 74HC595

Ok, you also have a multiplication in your code, which has the same problem of using System variables.

Change it to this ...

Code:

; B = Char * 16 ' Lower 4 Bits Shift B = Char << 1 B = B << 1 B = B << 1 B = B << 1

Added:

Attachment 7208

The 16F628A only has a 4Mhz internal oscillator, yours was running at 8Mhz, and your circuit wouldn't work at 4Mhz.
I had to increase the capacitors to 4.7nF

Code:

@ DEVICE pic16F628A, intOSC_osc_noclkout, WDT_OFF, PWRT_OFF, BOD_OFF, MCLR_OFF DEFINE OSC 4 Serial_Pin var PortA.3 B0 var byte B1 VAR Byte OUTPUT Serial_Pin CMCON = 7 B0 = 0 B1 = 255 INCLUDE "One_Wire_74HC595.pbp" ; *** Include MUST be AFTER LCD Pin assignments * ;----[ Your Main program starts here ]---------------------------------------- LCDOUT $FE, 1 LCDOUT $FE, 1, IHex 255 Pause 2000 Main: LCDOUT $FE,$80,"B0 = ",DEC B0," " LCDOUT $FE,$C0,"B1 = ",DEC B1," " B0 = B0 + 1 B1 = B1 - 1 PAUSE 1000 GOTO Main

Re: Driving a 2x16 LCD with only One Pin and 74HC595

Awesome, Darrel

Yes, that's it!!

Can I also write:

B = Char
B = B << 4

I tested it once more with the Pauseus...it also runs.:confused:
Would you still recommend to use the DelayUS Command in whole code?

Thanks in advance!

Most definitely, you must not use PAUSEUS.

And no, you cant use B = B << 4
The CPU can only shift one bit at a time. So it requires a loop and a variable to count the number of shifts.
That uses a SYSTEM variable.

And there are two more issues that cause instability.

1) The reason I had to change the capacitors is the @ NOP which changes timing with different oscillator frequencies.
It should be replaced with ...

Code:

@ DelayUS 1

And the capacitors should be left at 4.7nF
That way it will work with all PBP OSC frequencies.
.
2) And this statement also affects System variables, for the same reason as B =B << 4 ...

Code:

D = B >> E

It could be replaced with ...

Code:

F var byte G var byte ;D = B >> E F = E G = B ShiftLoop G = G >> 1 F = F - 1 IF F != 0 THEN ShiftLoop D = G.0

Although I have a feeling it can be reduced somehow.
.

I think that should give a stable include file.
At least it works well here.

But I'll add that you are using common variable names in the include like ...A, B, C etc.
That means that when someone uses your include, they cannot use those variable names.
It's better to make unique variable names that are unlikely to be used by the person using your code.
Descriptive names are the best. Try to use a name that describes what the variable is used for.

Re: Driving a 2x16 LCD with only One Pin and 74HC595

Ok, with the variable name you are right!

About Point 2:

Could be this a better Solution:

Code:

'******************************Shift_74HC595*********************************** F = B E = 7 Repeat ;D = B >> E ASM rlf _F, F BTFSS STATUS, C BCF _D BTFSC STATUS, C BSF _D ENDASM E = E - 1 SELECT CASE D CASE 1 Serial_Pin = 0 @ DelayUS 1 ' min 1 µs for 1 Serial_Pin = 1 @ DelayUS 15 ' min 15 µs Case 0 Serial_Pin = 0 @ DelayUS 15 ' min 15 µs for 0 Serial_Pin = 1 @ DelayUS 30 ' min 30 µs END SELECT Until E = 0 'Latch Serial_Pin = 0 @ DelayUS 200 ' min 200 µs for Latch Serial_Pin = 1 @ DelayUS 300 ' min 300 µs Next Return

Thanks in advance!

Re: Driving a 2x16 LCD with only One Pin and 74HC595

Here I'm again.

Again to my last post:
I think over it again and C Flag is also an System Variable.
Also too unsuitable.

What have I done:

I rewrite the code once again.
I change the Variable Name's an insert your code from Statement 2.
Could it be, that there is an small mistake.

Code:

F var byte G var byte ;D = B >> E F = E G = B ShiftLoop ;G = G >> 1 G = G << 1 F = F - 1 IF F != 0 THEN ShiftLoop ;D = G.0 D = G.7

Once Again here is the code

Code:

Char_Temp var byte ShiftOut_Steps var byte Count_ShiftOut_Steps var byte ShiftLoop_Steps Var byte Bit_Shift Var byte Readout_Bit var bit INCLUDE "VirtualPort.bas" LCD_DATAUS CON 2000 LCD_COMMANDUS CON 50 Goto Over_One_Wire_74HC595 ;===============( DO NOT Change anything below this line )==================== ASM ; Make sure HighJack has been installed in PBP's .LIB file ifndef LCDOUT_HIGHJACKED error "HighJacked-LCDOUT Not found in PBPPIC??.LIB" endif ENDASM DEFINE HJ_LCDOUT _LCDsend ; Redirect PBP's LCDOUT to LCDsend: Subroutine ;----[Send a byte to the Virtual LCD PORT]------------(DO NOT Change)--------- TempChar var byte Char VAR Byte LCD_Initialized VAR FLAGS.1 RSS VAR FLAGS.0 ; LCD RS State ;----[ This routine is called once for every character sent by LCDOUT ]------- LCDsend: @ MOVE?AB _TempChar ; Get char sent by LCDOUT, in WREG if !LCD_Initialized then LCD_Init ; Make sure LCD was Initialized LCDAfterInit: if TempChar = $FE then RSS=0 : goto LCDsendDone ; next char is Command Char = TempChar LCDsendCOM: Goto ShiftLoop_Char After_ShiftLoop_Char: IF RSS = 0 then ; Is a Command IF Char = 1 then CommandDelay ; Long delay for Clear Screen IF Char = 2 then CommandDelay ; Long delay for Home @ DelayUS _LCD_DATAUS ; Short delay for everything else goto DelayDone else @ DelayUS _LCD_DATAUS ; Short delay for Data goto DelayDone endif CommandDelay: @ DelayUS _LCD_COMMANDUS DelayDone: if LCD_Initialized then RSS = 1 ; Set RS to Data next time LCDsendDone: return ;----[Initialize the LCD]-------------------(DO NOT Change)------------------- LCD_Init: ShiftOut_Steps = 2 Char = $33 : gosub LCDsendCOM : @ DelayUS 5000 gosub LCDsendCOM : @ DelayUS 100 gosub LCDsendCOM : @ DelayUS 100 Char = $22 : gosub LCDsendCOM ; Start 4-bit mode ShiftOut_Steps = 5 Char = $28 : gosub LCDsendCOM ; Function Set, 4-bit, 2-line, 5x7 Char = $0C : gosub LCDsendCOM ; Display ON Char = $06 : gosub LCDsendCOM ; Entry Mode LCD_Initialized = 1 ; LCD has been Initialized goto LCDAfterInit ;----[Send it to 74HC595]-------------------(DO NOT Change)------------------- ShiftLoop_Char: For Count_ShiftOut_Steps = 0 to ShiftOut_Steps ' For To Loop SELECT CASE Count_ShiftOut_Steps CASE 0 Char_Temp = Char & %11110000 ; Isolate Upper 4 Bits If RSS = 1 Then : Char_Temp = Char_Temp | %00000100 ; Set RS Bit CASE 1, 4 Char_Temp = Char_Temp | %00001000 ; Set Enable Bit CASE 2, 5 Char_Temp = Char_Temp ^ %00001000 ; Toggel Enable Case 3 Char_Temp = Char << 1 ; Shift Up Lower 4 Bits Char_Temp = Char_Temp << 1 Char_Temp = Char_Temp << 1 Char_Temp = Char_Temp << 1 If RSS = 1 Then : Char_Temp = Char_Temp | %00000100 ; Set RS Bit END SELECT Bit_Shift = Char_Temp ;----[Shift_Routine_74HC595 ]---------------(DO NOT Change)------------------- ShiftLoop_Steps = 7 ShiftLoop: Readout_Bit = Bit_Shift.7 SELECT CASE Readout_Bit CASE 1 Serial_Pin = 0 : @ DelayUS 1 ; min 1 µs for 1 Serial_Pin = 1 : @ DelayUS 15 ; min 15 µs Case 0 Serial_Pin = 0 : @ DelayUS 15 ; min 15 µs for 0 Serial_Pin = 1 : @ DelayUS 30 ; min 30 µs END SELECT Bit_Shift = Bit_Shift << 1 ShiftLoop_Steps = ShiftLoop_Steps - 1 IF ShiftLoop_Steps != 0 THEN : Goto ShiftLoop ;Latch Serial_Pin = 0 : @ DelayUS 200 ; min 200 µs for Latch Serial_Pin = 1 : @ DelayUS 300 ; min 300 µs 'Count_ShiftOut_Steps = Count_ShiftOut_Steps + 1 ' for If Then Request 'IF Count_ShiftOut_Steps != ShiftOut_Steps Then : goto ShiftLoop_Char ' for If Then Request Next ' For To Loop Goto After_ShiftLoop_Char Over_One_Wire_74HC595:

I also wanted to replace the For To Loop with an normal If - Then request, because of the Usage of System Variables; or is there neither.
It also works well but when I simulate it, it takes too much CPU Usage and Runs very slow.
Using an Repeat Until Loop also.
With an For To Loop the simulation is better.

But which Loop is the best, when one think only about the Usage in an Microcontroller?
What did you say. Is it OK or is there something which one can also improve.

Thanks in advance!

Re: Driving a 2x16 LCD with only One Pin and 74HC595

STATUS,C is not a PBP system variable. You can use it.

FOR loops, REPEAT/UNTIL, WHILE/WHEN, DO/LOOP all do not use the system vars (as long as the test condition is = or !=).
They will use system vars if the test condition is <, <=, >, >= etc.

Speed differences between any of the loop types will not be significant on a real chip.
The major slow down with this interface is the timing required to activate inputs on the 595 using the capacitors.
All those delays in the code make writing to the LCD very slow.

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Re: Driving a 2x16 LCD with only One Pin and 74HC595

Your include looks better with the new variable names.
I ran it this morning, and it seems to be working.

Have you looked at the signals going to the 595 on a scope? :eek:
Scary stuff to be putting in a digital chip.

Yellow is the serial data.
Blue is after the 1.5K resistor.
Magenta is after the 33K resistor.

Attachment 7209

And you can see that it takes 910 uS per nibble (1.82 mS per byte).

It would be interesting to see how it works on real hardware.

Re: Driving a 2x16 LCD with only One Pin and 74HC595

Hello Darrel,

yes your are right, very scary!

And yes I use the scope, because of controlling the puls length (µs).

What I have done again:

I reduce the code a little bit and I change/simplified some parts.

Code:

I replace this: Char_Temp = Char << 1 ; Shift Up Lower 4 Bits Char_Temp = Char_Temp << 1 Char_Temp = Char_Temp << 1 Char_Temp = Char_Temp << 1 with this: Char_Temp = Char & %00001111 ; Shift Up Lower4 Bits @ swapf _Char_Temp ,F

Also I reduce the Upper an Lower Nibbel Part from 6 to only 4 Steps.

Code:

SELECT CASE Count_ShiftOut_Steps CASE 0 Char_Temp = Char & %11110000 ; Isolate Upper 4 Bits If RSS = 1 Then : Char_Temp = Char_Temp | %00000100 ; Set RS Bit CASE 1, 3 Char_Temp = Char_Temp | %00001000 ; Set Enable Bit Case 2 Char_Temp = Char & %00001111 ; Shift Up Lower4 Bits @ swapf _Char_Temp ,F If RSS = 1 Then : Char_Temp = Char_Temp | %00000100 ; Set RS Bit END SELECT

Because Toggle the Enable Bit again is not necessary.

Further, I change (Post 6, Point 2...."Although I have a feeling it can be reduced somehow")

Code:

This: ;----[Shift_Routine_74HC595 ]---------------(DO NOT Change)------------------- ShiftLoop_Steps = 7 ShiftLoop: Readout_Bit = Bit_Shift.7 SELECT CASE Readout_Bit CASE 1 Serial_Pin = 0 : @ DelayUS 1 ; min 1 µs for 1 Serial_Pin = 1 : @ DelayUS 15 ; min 15 µs Case 0 Serial_Pin = 0 : @ DelayUS 15 ; min 15 µs for 0 Serial_Pin = 1 : @ DelayUS 30 ; min 30 µs END SELECT Bit_Shift = Bit_Shift << 1 ShiftLoop_Steps = ShiftLoop_Steps - 1 IF ShiftLoop_Steps != 0 THEN : Goto ShiftLoop ;Latch Serial_Pin = 0 : @ DelayUS 200 ; min 200 µs for Latch Serial_Pin = 1 : @ DelayUS 300 ; min 300 µs Next To This: ;----[Shift_Routine_74HC595 ]---------------(DO NOT Change)------------------- ShiftLoop: For ShiftLoop_Steps = 0 to 6 @ rlf _Bit_Shift, F ; Shift 1.Pos left If STATUS.0 = 1 Then ; Carry Flag Serial_Pin = 0 : @ DelayUS 1 ; min 1 µs for 1 Serial_Pin = 1 : @ DelayUS 15 ; min 15 µs else Serial_Pin = 0 : @ DelayUS 15 ; min 15 µs for 0 Serial_Pin = 1 : @ DelayUS 30 ; min 30 µs endif next ;Latch Serial_Pin = 0 : @ DelayUS 200 ; min 200 µs for Latch Serial_Pin = 1 : @ DelayUS 300 ; min 300 µs Next

Up to now, the code runs very good. (I Think a little bit better then before.)
But sometimes when I simulate it on the PC, after some time, the LCD shows only cryptic characters.
Then I have to restart the simulation again an all works fine.

What du you think, is there something one can improve?

Thanks in advance!

Re: Driving a 2x16 LCD with only One Pin and 74HC595

Note also there will be a wide variation of timings across components, a wide variation of chip sensitivity, and a sensitivity to clock speed, temperature, power supply voltage, data rates, etc. etc. This approach is "O.K." for a hobby project, but it would be a very bad idea to try to use it in a commercial project, especially anything that might see volume.

Not to rain on your parade, but given you can get PIC devices with fewer pins and at lower cost than a 74HC595, you would be further ahead to create a dedicated display driver PIC that you can send data to by 1 pin serial. Fewer components too, and rock solid communications.

Re: Driving a 2x16 LCD with only One Pin and 74HC595

Hello,

Yesterday I tested it with an 12F675 at 4 Mhz intOSC and till now it runs stable and fast.:smile:
When I less busy, I will test it out with other frequencies.

But i have yet again an comprehension question to this code:

Code:

LCDsend: @ MOVE?AB _TempChar ; Get char sent by LCDOUT, in WREG if !LCD_Initialized then LCD_Init ; Make sure LCD was Initialized LCDAfterInit: if TempChar = $FE then RSS=0 : goto LCDsendDone goto DONE ; next char is Command Char = TempChar LCDsendCOM: Goto ShiftLoop_Char After_ShiftLoop_Char: IF RSS = 0 then ; Is a Command IF Char = 1 then CommandDelay ; Long delay for Clear Screen IF Char = 2 then CommandDelay ; Long delay for Home @ DelayUS _LCD_DATAUS ; Short delay for everything else goto DelayDone else @ DelayUS _LCD_DATAUS ; Short delay for Data goto DelayDone endif CommandDelay: @ DelayUS _LCD_COMMANDUS DelayDone: if LCD_Initialized then RSS = 1 ; Set RS to Data next time LCDsendDone: bsf STATUS, C ; Set no timeout for Serout2mod return

When i compare these steps with them in pbppic14.lib, than i note that in the upper code some parts (Red marked) not exist, like in the library code.

@ Darrel:
Are these Commands not necessary or why didn't you include them?

Further I would shrink this code to this:

Code:

LCDsend: @ MOVE?AB _TempChar ; Get char sent by LCDOUT, in WREG if !LCD_Initialized then LCD_Init ; Make sure LCD was Initialized LCDAfterInit: if TempChar = $FE then RSS=0 : goto LCDsendDone ; next char is Command Char = TempChar LCDsendCOM: Goto ShiftLoop_Char After_ShiftLoop_Char: if LCD_Initialized then RSS = 1 ; Set RS to Data next time LCDsendDone: return

Because of the fact, that the shifting time of 1 byte needs about 2 - 4ms, it is not nessesary to include extra Delays for Data or Commands.

Can I do it in this way?

Thanks in advance!

Re: Driving a 2x16 LCD with only One Pin and 74HC595

If you use GOTO DONE, it limits the use of your include to 14-bit devices.
In the 18F library, it's called DUNN.

There's no need to use DONE, since the FSR hasn't been changed, and RETURN resets the BANK to 0 anyhow.

The bsf STATUS, C is only required if the end user is using the SEROUT2 command with a Flow Control Pin.
My observations have concluded that nobody uses that function. Or if they understand how to use Flow Control, they probably aren't using LCD_AnyPin. :)

However, to cover ALL the bases ... you are correct! bsf STATUS, C should be there. But it needs an @ sign.

As for removing the delays ... I don't think that's a good idea.
The measurement I took previously was 1.8 mS per byte.
Most good LCD's take 1.6 mS for a Clear Screen, so it would be fine (with a good LCD).
But there are LCD's that take longer, 2.4 mS is not uncommon.

You could remove the LCD_DATAUS part since it will always be under 1.8 mS.

But I think the ability to add delays for LCD_COMMANDUS should remain in the program.
You can easily set LCD_COMMANDUS to 0 in the main program for normal displays.
For slower LCD's, just set it to the difference of say 2.4 mS - 1.8 ms = 0.6 mS or 600 uS.

7 Attachment(s)

Re: Driving a 2x16 LCD with only One Pin and 74HC595

Thanks Darrel,

now I'm wiser, again thanks.

With the delays......

To shift out one byte (Data or Command) after LCDInit it needs 4 Steps.
One Step require a time nearly 910µs - 1ms.
That makes nearly 4ms. => No extra Delay necessary. Right?

The First 4 commands in the LCD_Init part needs only 2 Steps, because only the 4 upper bits shifted out.
There, I'm agree with you that the delay should be longer.

Could I place them here: ?

Code:

LCD_Init: ShiftOut_Steps = 1 Char = $33 : gosub LCDsendCOM : @ DelayUS 5000 gosub LCDsendCOM : @ DelayUS 600 gosub LCDsendCOM : @ DelayUS 600 Char = $22 : gosub LCDsendCOM : @ DelayUS 600 ; Start 4-bit mode ......... ......... .........

Further I tested again with other frequencies.
I use 8 Mhz and a 20 Mhz quarz.
Also there are, no problems. It runs stable.

What I find out is that it is absolute necessary, to add an capacitor between +V and GND of the 74HC595.
I use an 100nF.
Otherwise you get sometimes error in displaying the right things.:smile:

The capacitor for the Latch Pulse, I would change back to 2.2nF. And the capacitor for the 1 or 0 Pulse should be left at 4.7nF.

Here are some picture make with my mini DSO.:rolleyes:

Clock Pulse
Attachment 7226

Pulse 1 or 0 with 2.2nF
Attachment 7228 Attachment 7232

Pulse 1 or 0 with 4.7nF
Attachment 7229 Attachment 7233

Latch 2.2nF & Latch 4.7nF
Attachment 7231 Attachment 7230

Re: Driving a 2x16 LCD with only One Pin and 74HC595

Quote:

Originally Posted by struppi81

To shift out one byte (Data or Command) after LCDInit it needs 4 Steps.
One Step require a time nearly 910µs - 1ms.
That makes nearly 4ms. => No extra Delay necessary. Right?

No, each byte whether it's a command or data requires two nibbles at 910 uS or 1.82 mS total.

You need the delays!

And I would leave the initialization timing the same.
It only happens once per power-on, so you're not saving any time during normal operations.

Re: Driving a 2x16 LCD with only One Pin and 74HC595

Now im confused:confused:

LCD_Init _Only the First 4 Commands (2 Steps):

Step1: shiftout 1 byte.
Enable_High + Data high nibble + Latch => nearly 910µs (Delay at the next Command)

Step2: shiftout 1 byte
Enable_Low + Data high nibble + Latch => nearly 910µs (Delay at the next Command till Latch)

=> 1,8 µs => extra delay necessary.

Next Command....

The 3 others Commands 4 Steps ; (see after LCD Init)

After LCD Init (4 Steps): (Commands without RS)

Step1: shiftout 1 byte.
RS + Enable_High + Data high nibble + Latch => nearly 910µs (Delay at the next Command or Data)

Step2: shiftout 1 byte
RS + Enable_Low + Data high nibble + Latch => nearly 910µs (Delay at the next Command or Data)

Step3: shiftout 1 byte
RS + Enable_High + Data low nibble + Latch => nearly 910µs (Delay at the next Command or Data)

Step4: shiftout 1 byte
RS + Enable_Low + Data low nibble + Latch => nearly 910µs (Delay at the next Command or Data till Latch)

=> 3,6µs

Next Command or Data....

:confused:

Re: Driving a 2x16 LCD with only One Pin and 74HC595

Or I'm confused, not sure.
I see how it takes 4 "steps" just to toggle the E line.

But, the LCD will not accept any data or commands while it is busy.
Even though it takes 4 steps ... you are clocking in the first nibble after the first 2 steps 1.82 mS.

The HD44780 datasheet timing diagrams show that the first nibble can't be clocked in until after the last command is complete (not busy).
There is no text that confirms it, but that's what the timing diagrams show.

1 Attachment(s)

Re: Driving a 2x16 LCD with only One Pin and 74HC595

OK,

now I post my Final, good working code.

I implement the ability to add delays for LCD_COMMANDUS in the main programm and the part, if somebody want to use SEROUT2 with a Flow Control Pin. (I don't have test it yet)

With my LCD's, I could set the LCD_COMMANDUS Value to 0.

It would be very interesting if somebody could test it out with an slower LCD and post which value he have to set or general experiences.

A big thanks to Darrel Taylor.

Zip File implements:
One_Wire_74HC595_Main.pbp
One_Wire_74HC595.bas
VirtualPort.bas

Re: Driving a 2x16 LCD with only One Pin and 74HC595

Hello,:)
I desperately looking for a simple code
use an LCD via a 74HC595 or 3 wire.
why is it so difficult to make a code with
LCDOUT the order?
mimie64:confused:

Re: Driving a 2x16 LCD with only One Pin and 74HC595

Hello.

In the simulation proteus, sometimes appear strange characters, is this normal?