Post by thread:LCD Problem

Does your code hang the lcd off one port (port b). I desperately need some code that frees porta completely but uses lcd on port b. Thanks Tim At 13:07 03/02/97 +0200, you wrote: {Quote hidden}>>> >>> Hi PICers, >>> I have a trouble. A big trouble. I want to hook a LCD module to pic16c84. >>> I build a schematics - it uses 8 bit interface. I get Microchip application >>> note AN??? (sorry can't remember the number). I port it for 16c84, program >>> the chip and ...nothing happens. I use 2x20 LCD with LED backlight, so I >>> carefully examine LCD data sheet - it says Vo (LCD driving voltage) must be >>> 0..5V, use 10K-20K pot between 5v and ground - well evereting was OK. After >>> that I wrote a simple program that tests every line - evereting was OK, >>> but LCD still displays nothing - only the backlite is on but LCD is empty. >> > Hi PICers. It's me again. Thanks to all who reply. Finally I solve the problem. >I change the LCD and it WORKS, so I think the old LCD is gone. > >Best regards, > Greg > ------------------------------------------------------------------ If you can read this, it is the end of the message! My web pages are at http://web.ukonline.co.uk/members/tim.kerby/ My PIC site is at web.ukonline.co.uk/members/tim.kerby/pic/ It needs your projects! ------------------------------------------------------------------

In a message dated 97-02-03 15:24:51 EST, you write: << Does your code hang the lcd off one port (port b). I desperately need some code that frees porta completely but uses lcd on port b. Thanks Tim >> Tim, I have used this routine with some success, It uses only the portB on a 16C84. It is in the form of an include file. In your source just put : Include LCD4.h. It is a derivative (if not a direct copy) of the MCHIP app note. Hope this helps David Duley V.P. DreiTek Inc. ;************************************************************ ;Use this file for 4 bit LCD interfaces ;************************************************************ lcddata equ Port_B ; these two lines make it easy to port LCD lcdcntrl equ Port_A ; routines to the PIC 57 or whatever. LCD_DATA equ lcddata LCD_CNTL equ lcdcntrl ;************************************************************ ; Bit Definitions ;************************************************************ E equ 2 ;LCD enable strobe RS equ 3 ;LCD register select RW equ 4 ;LCD read write select lcd_strobe equ 03fh ;LCD strobe pulse width number_of_chars equ .20 ;# of characters on line Disp_On equ 0x00C ;Display on Disp_On_C equ 0x00E ;Display on Cursor on Disp_On_B equ 0x00F ;Display on cursor blink Disp_Off equ 0x008 ;Display off Clr_Disp equ 0x001 ;Clear display Entry_Inc equ 0x006 Entry_Inc_S equ 0x007 Entry_Dec equ 0x004 Entry_Dec_S equ 0x005 DD_RAM_ADDR equ 0x080 ;Least significant 7 bit are for address DD_RAM_UL equ 0x080 ;Upper Left corner of the display Busy_Check movlw TrisMaskB ;get I/O assignments bsf status,rp0 ;bank 1 select iorlw 0xf0 ;deal with only the upper nibble movwf Tris_B ;setup LCD to read data bcf status,rp0 bcf LCD_CNTL,RS bsf LCD_CNTL,RW call lcd_wait bsf LCD_CNTL,E ;get upper nibble bcf LCD_CNTL,E movf LCD_DATA,w ;get upper nibble of display data andlw 0xf0 ;mask off the lower nibble movwf temp bsf LCD_CNTL,E ;get lower nibble bcf LCD_CNTL,E swapf LCD_DATA,W andlw 0x0f ;mask off upper nibble iorwf temp,f btfsc temp,7 ;check busy flag goto Busy_Check ;do it again if still busy bcf LCD_CNTL,RW movlw TrisMaskB bsf status,rp0 Movwf Tris_B bcf status,rp0 return LCD_init ;init LCD display call lcd_wait bcf lcdcntrl,RS ;Set register select to command regs bcf lcdcntrl,E ;Clear the lcd module enable bit. bcf lcdcntrl,RW ;Clear the lcd module Read/Write bit. call lcd_wait movlw 0x020 ;set lcd module for 4 bit operation movwf lcddata bsf LCD_CNTL,E bcf LCD_CNTL,E call lcd_wait movlw 0x020 ;set lcd module for 4 bit operation movwf lcddata bsf LCD_CNTL,E bcf LCD_CNTL,E call lcd_wait movlw 0x080 ;set lcd module for 8 bit operation movwf lcddata bsf LCD_CNTL,E bcf LCD_CNTL,E movlw Disp_On ;set lcd on, cursor off call SEND_CMD movlw Clr_Disp ;Clear Display call SEND_CMD movlw Entry_Inc ;Set to increment display call SEND_CMD movlw DD_RAM_ADDR call SEND_CMD movlw number_of_chars movwf chcount bcf flag,7 goto lcd_wait ;******************************************************************* ;* The LCD Module Subroutines * ;******************************************************************* ; ;******************************************************************* ;*SendChar - Sends character to LCD * ;*This routine splits the character into the upper and lower * ;*nibbles and sends them to the LCD, upper nibble first. * ;******************************************************************* ; SEND_CHAR MOVWF CHAR ;Character to be sent is in W call Busy_Check movf CHAR,w ANDLW 0xF0 ;Get upper nibble movwf CharSave movf LCD_DATA,w andlw 0x0F iorwf CharSave,w ;only affect upper nibble of LCD_DATA MOVWF LCD_DATA ;Send data to LCD BSF LCD_CNTL, RS ;Set LCD to data mode BSF LCD_CNTL, E ;toggle E for LCD BCF LCD_CNTL, E SWAPF CHAR, w ANDLW 0xF0 ;Get lower nibble movwf CharSave movf LCD_DATA,w andlw 0x0F iorwf CharSave,w ;only affect upper nibble of LCD_DATA MOVWF LCD_DATA ;Send data to LCD BSF LCD_CNTL, E ;toggle E for LCD BCF LCD_CNTL, E return ;******************************************************************* ;* SEND_CMD - Sends command to LCD * ;* This routine splits the command into the upper and lower * ;* nibbles and sends them to the LCD, upper nibble first. * ;******************************************************************* SEND_CMD MOVWF CHAR ; Character to be sent is in W call Busy_Check movf CHAR,w ANDLW 0xF0 ; Get upper nibble movwf CharSave movf LCD_DATA,w andlw 0x0F iorwf CharSave,w ;only affect upper nibble of LCD_DATA MOVWF LCD_DATA ; Send data to LCD BCF LCD_CNTL,RS ; Set LCD to command mode BSF LCD_CNTL,E ; toggle E for LCD BCF LCD_CNTL,E SWAPF CHAR,w ANDLW 0xF0 ; Get lower nibble movwf CharSave movf LCD_DATA,w andlw 0x0F iorwf CharSave,w ;only affect upper nibble of LCD_DATA MOVWF LCD_DATA ; Send data to LCD BSF LCD_CNTL,E ; toggle E for LCD BCF LCD_CNTL,E return ;******************************************************************** ; This routine clears the LCD display * ;******************************************************************** dispclear bcf lcdcntrl,RS movlw 01h ;clear lcd display call SEND_CMD movlw 06h ;set entry mode on lcd module call SEND_CMD movlw number_of_chars movwf chcount bcf flag,7 ;******************************************************************** ; This routine waits 12ms for erase ans write commands * ;******************************************************************** lcd_wait movlw .48 movwf count wwait movlw 0ffh movwf temp wwait1 decfsz temp,f goto wwait1 decfsz count,f goto wwait retlw 0 ; LCD_Out ;put data at current cursor position on LCD call SEND_CHAR decf chcount,f retlw 0 set1st ;set display to display on the first line movlw 080h ;address cursor to 1st position call SEND_CMD movlw number_of_chars ;reset character counter movwf chcount bcf flag,7 ;reset line flag retlw 0 set2nd ;set display to display on the second line movlw 0c0h ;address cursor to 1st position 2nd line call SEND_CMD movlw number_of_chars ;reset character counter movwf chcount bsf flag,7 ;set line flag retlw 0

Hi all, I need your help with an LCD that I am trying to use. I bought it surplus from Marlin P. Jones ( http://www.mpja.com ). It is a TRULY SEMICONDUCTOR model MC162-1 It is a text LCD/driver/controller board. Sorry in advance for writing a veritable book here, but I thought it best to fully describe my problem. I have a datasheet for it, but as always, there are a few things which the datasheet doesn't explain. For example, there is an input signal/voltage listed as "Vo" on the pinout, and listed as an input on the block diagram, but it is mentioned nowhere else. The absolute maximum ratings only mention two supplies, Vdd and Vlcd, both of which should be 5V. Now, here's the second thing I don't understand: there are actually two terminals for Vlcd, positive and negative. Why two? Why wouldn't it just be referenced to Vss? Especially because its maximum input rating is given in terms of Vdd (Vdd+0.3V). There are also two additional solder pads on the side of the LCD board, marked + and -, which are never mentioned in the datasheet. The "-" one is connected internally to Vlcd(-), but the "+" one is not connected to either Vdd, Vss, or Vlcd(+). This is a parallel interface LCD and I have code running on a PIC to send the correct data, at least according to the datasheet. The result is that I see nothing at all on the LCD screen. Nothing turns opaque. The datasheet is also not clear about whether or not the Enable signal is active high or low. It appears that a high-low transistion causes a load of the data, but it shows it in the low state before the data transfer, it goes high before the data is valid, drops to low while the data is valid, and goes back high at the end of the transfer,so it is not clear to me what value it should assume during idle. I have tried treating the E as both active high and active low. I have also tried applying 5V to only Vdd, to both Vdd and Vo, to both Vdd and Vlcd(+) (with and without Vlcd(-) being attached), to Vdd and the undocumented + terminal, and to all Vo, Vdd, Vlcd(+), and the undocumented + terminal, and none of these combinations has caused anything visible to happen. I guess the next step would be to try reading back what I have written to the display memory, to see if at least the LSI is running. However, I am hesitant to write extra code if there is a simple solution. One last note: The datasheet is for model MC162-1, but the board itself actually says MCC162A4-5. I hope that they are compatible <G>. Thanks very much, Sean BTW, in case you are wondering what I am making, it is a dual (pos/neg) variable power supply/frequency counter/function generator all in one. It will have pretty much only a PIC and a MAXIM function generator IC in it. The LCD will read out either internal or external frequency, as well as the voltage on the two supply outputs. I need this instrument to facilitate my work on the PIC-based DSO because I currently do not have any good adjustable frequency source, or pos/neg voltage supply, both of which are needed to troubleshoot my scope input amp design and trigger circuit. +--------------------------------+ | Sean Breheny | | Amateur Radio Callsign: KA3YXM | | Electrical Engineering Student | +--------------------------------+ Save lives, please look at http://www.all.org Personal page: http://www.people.cornell.edu/pages/shb7 spam_OUTshb7TakeThisOuTcornell.edu Phone(USA): (607) 253-0315 ICQ #: 3329174

Peters, YOU ARE THE MAN! <VBG> It worked as soon as I hooked up that pot. I would never have believed it was that simple. There it is , that little display saying "Hello" at me, and I can even adjust the contrast now! Thanks very much, Sean At 07:35 PM 10/7/98 -0700, you wrote: {Quote hidden}>Hi, >Vo voltage for the LCD contrast adjustment, You need a 10-5 KOhm trimmerpot >between Vdd and Vss the wiper goes to >Vo. There are more tricky circuits to control the contrast ( contrast is >very temperature dependent ) but this is the easiest way to check. Do not >connect any data line, if your PS rising time is OK it will reset itself >and adjusting the pot You must see all dots in one line are on. >The reason of using different pins for the background LCD because they usual >current is 100-300 mA and most of the designers do not want to dissipate >that thru the 5V power supply . >I have Optrex data sheet better discription of the data lines. Let me know >and I will fax You, >Cheers, >Peters > +--------------------------------+ | Sean Breheny | | Amateur Radio Callsign: KA3YXM | | Electrical Engineering Student | +--------------------------------+ Save lives, please look at http://www.all.org Personal page: http://www.people.cornell.edu/pages/shb7 .....shb7KILLspam@spam@cornell.edu Phone(USA): (607) 253-0315 ICQ #: 3329174

Hi Sean, I also bought the same display, and also the 16x1. Assuming it to be a standard type, I just connected it according to David Benson's Book PIC'n up the Pace. The book provides a fairly complete treatment of these displays, both 16x1, and 16x2 in a very understandable form, with complete PIC software code. At 6:24 PM 10/7/98, Sean Breheny wrote: >Hi all, ...large snip... >For example, there is an input signal/voltage >listed as "Vo" on the pinout, and listed as an input on the block diagram, >but it is mentioned nowhere else. The absolute maximum ratings only mention >two supplies, Vdd and Vlcd, both of which should be 5V. Now, here's the >second thing I don't understand: there are actually two terminals for Vlcd, >positive and negative. Why two? Why wouldn't it just be referenced to Vss? >Especially because its maximum input rating is given in terms of Vdd >(Vdd+0.3V). from the book the pins from left to right ( with the display facing you) are 1 - GND 2 - +5V 3 - Gnd -> voltage for display contrast (I've seen a 2k5 ohm voltage divider for contrast but not tried it.) 4 - RS 5 - R/-W -> Grounded for most apps 6 - E -> Positive logic (125 micro sec pulse) 7 - D0 8 - D1 9 - D2 10 - D3 11 - D4 12 - D5 13 - D6 14 - D7 15 - Not used | 16 - Not used | | I've taken these to be involved with backlighted displays "+" - Not used | "-" - Not used | >There are also two additional solder pads on the side of the LCD board, >marked + and -, which are never mentioned in the datasheet. The "-" one is >connected internally to Vlcd(-), but the "+" one is not connected to either >Vdd, Vss, or Vlcd(+). > This maybe for the backlight option ? >This is a parallel interface LCD and I have code running on a PIC to send >the correct data, at least according to the datasheet. The result is that I >see nothing at all on the LCD screen. Nothing turns opaque. Is pin 3 low? >The datasheet >is also not clear about whether or not the Enable signal is active high or >low. It appears that a high-low transistion causes a load of the data, but >it shows it in the low state before the data transfer, it goes high before >the data is valid, drops to low while the data is valid, and goes back high >at the end of the transfer,so it is not clear to me what value it should >assume during idle >I have tried treating the E as both active high and active low. See above ...snip... >I guess the next step would be to try reading back what I have written to >the display memory, to see if at least the LSI is running. However, I am >hesitant to write extra code if there is a simple solution. There are some tricks to allow the display time to initialize after powerup. > >One last note: The datasheet is for model MC162-1, but the board itself >actually says MCC162A4-5. I hope that they are compatible <G>. ? ....snip... regards, Heinz

Thanks Heinz, As you probably have seen by now in my other post, the problem is now fixed and it had to do with the fact that I was not attaching a pot to Vo (the contrast pin). I do have one question for you, though. I have so far only displayed "Hello" on it on one line. Tomorrow, I should get a bit more time to play with it. Is there anything special needed to access the second line, or can I just continue to write chars and it will wrap around to the next line? Also, what is the address for the next line (does it just start with 16?) Thanks, Sean At 11:10 PM 10/7/98 -0500, you wrote: {Quote hidden}>Hi Sean, > >I also bought the same display, and also the 16x1. Assuming it to be a >standard type, I just connected it according to David Benson's Book PIC'n >up the Pace. The book provides a fairly complete treatment of these >displays, both 16x1, and 16x2 in a very understandable form, with complete >PIC software code. > +--------------------------------+ | Sean Breheny | | Amateur Radio Callsign: KA3YXM | | Electrical Engineering Student | +--------------------------------+ Save lives, please look at http://www.all.org Personal page: http://www.people.cornell.edu/pages/shb7 shb7KILLspamcornell.edu Phone(USA): (607) 253-0315 ICQ #: 3329174

At 11:18 PM 10/7/98, Sean Breheny wrote: >Thanks Heinz, > >As you probably have seen by now in my other post, the problem is now fixed >and it had to do with the fact that I was not attaching a pot to Vo (the >contrast pin). Great that the fix was so simple. >I do have one question for you, though. I have so far only displayed >"Hello" on it on one line. Tomorrow, I should get a bit more time to play >with it. Is there anything special needed to access the second line, or can >I just continue to write chars and it will wrap around to the next line? >Also, what is the address for the next line (does it just start with 16?) You got me, I over sold the book 8^o, but it did help make using the 16x2 self evident. I had only gotten as far as you ( getting the display to send simple messages, surprisingly always less than 9 characters ) and because I tried a 16x1, and a 16x2 display, I thought both were covered. I checked the book again and found that it only covered 16x1 displays. What it indicated was the first eight character addresses start at 0x80, the next 8 at 0xC0 (for a 16x1 display). When I sent more than 8 characters to the 16x2 display, using the 16x1 software the 9th and subsequent characters went to the next line. So the first group of 16 characters are addressed from 0x80 through 0x8F, and the next set of 16 characters start at 0xC0. Embarrassed, Heinz