Serial LCD Controller
@ January 14, 2009
- Control method: Serial Port, Microcontroller
- CPU: PIC16F628, PIC16F88, pic16f628a
- Power source: 5V
- Programming language: MBasic, Picbasic Pro
10 October 2009
I discovered a flaw in the current design that will only allow the controller to work with a connection to the computer and not to a microcontroller. I've updated the schematic below and will fix the controller design. I've added a project file below that also includes the fixed schematic.
If you look at the schematic you will notice that when you set the jumper to non-inverted so you can connect to a microcontroller for serial control it will not work. The reason is in the way I designed the circuit for both inverted/non-inverted RS232 control. Looking at the transistor in the circuit, the collector is held high through a 10K resistor. The collector feeds to the Rx pin on the PIC. When you set the jumper to non-inverted and attempt to send data to the PIC it won't work because the line is always tied high through R8 to 5V.
There is a fix and I have included it in the archive file below. There are two ways to do this:
1. If your board is already built and your intentions are to only use this LCD in a finished design and not attached to the computer then, snip the connection from R8 to 5V and the controller will only work in the non-inverted configuration.
2. Look at the included schematic in the archive and add the shown J2 jumper to your design which will allow you to select between the two types of communication.
04 October 2009
I have redesigned the LCD Controller and updated the code. The new schematics and code can be found below. I ported the code from MBasic to PicBasic Pro. I'll leave the old code up for those who still want it.
The files below are from a project that I have been working on for a serial LCD controller for a 4x20 line parallel display with the Hitachi chipset. I am also working on a USB design. In the picture of the demo board there is a wire jumper installed. This is because I screwed the pooch and somehow missed a crossed trace. I had to repair the board. In the download files the PCB files have been fixed. I'll upload some video of functionality when I get a chance.
The code and project files have been posted in the download links.
Project file downloads
Old code:
Power regulation board schematic
Demo application with sourcecode
05 October 2009 Project Files
PicBasic Pro PIC16F628A code for 16x2 character LCD
PicBasic Pro PIC16F628 code for 16x2 character LCD
PicBasic Pro PIC16F628A code for 20x4 character LCD
Archive containing test application, schematic, and PCB (ExpressPCB)
PicBasic Pro LCD Controller interface to Parallax GPS receiver
Ensure all the files are unzipped to the same folder. The include file that is referenced contains the fuse settings for the selected PIC chip.
I will be uploading a version soon that allows the type of LCD to be set. This will allow the same controller to be used for a variety of LCDs. I can't squeeze that functionality into a PIC16F628 chip without removing some of the current functionality. So, I am porting that over to a PIC16F88.
More to come...
Breadboard testing of the LCD controller
Software application for testing functionality
LCD controller schematic
A better view of the controller schematic can be downloaded from the link below:
http://picasaweb.google.com/lh/photo/LZac_OpDpd0lbB8jCWJL0Q
USB version of the LCD controller
A better view of the controller schematic can be downloaded from the link below:
http://picasaweb.google.com/lh/photo/_XtaXjprlNdzRaFHGrha_Q
Optional power supply schematic
A better view of the controller schematic can be downloaded from the link below:
http://picasaweb.google.com/lh/photo/Hp0EJqKk4PNbVm69Vd1p8g
Component layout
PCB with two controllers and the optional power supply
PCB bottom side
PCB top side
LCD prototype board component view
Prototype board attached to the back of a LCD
Netlist
Serial LCD Controller v1.4
----------------------------
C1 0.1uf
D1 1N4148
J1 16-pin Header
J2 4-pin Header, Right Angle
J3 3-pin Header
J4 6-pin Header. Right Angle
JP1 Shorting Jumper
Q1 2N2222
Q2 2N2222
R1 1M
R2 10k
R3 1k
R4 22k
R5 15
R6 10k Potentiometer
R7 1k
R8 10k
U1 PIC16F628
X1 20Mhz
HD44780 20x4 LCD Module Display
Netlist
USB BUS Powered LCD Controller
-------------------------------
C1 0.1uF
C2 10nF
C3 10uF
C4 0.1uF
C5 0.1uf
D1 1N4148
F1 500mA, Ferrite Bead
J1 USB Type B, Digikey 787780-1-ND
J2 ICSP, 6-Pin, Right Angle Header
J3 LCD Connector, 16-Pin Header
J5 2-Pin Header
J6 2-Pin Header
JP2 Shorting Jumper
JP3 Shorting Jumper
LED1 RED
LED2 GREEN
Q1 2N2222
R1 330
R2 330
R3 1M
R4 10k
R5 15
R6 1k
R7 10k
SW1 Power, SPDT
U1 FT232RL
U2 PIC16F628
X1 20Mhz
*NOTE* All resistors on the controller board are 1/8 watt
Netlist
5V Power Regulation v1.0
-------------------------
C1 10uf
C2 0.1uf
C3 10uf
D1 1N4004
D3 1N4004
J1 Power Jack
J2 3-pin header
LED1 Light Emitting Diode
R1 220
SW1 SPDT Slide Switch
VR1 LM7805
*NOTE* All resistors on the power board are 1/4 watt
You can do a search on eBay for the LCDs and you will find them listed for as cheap as $5.00 minus shipping.
04 October 2009 - Redesigned Controller
I have redesigned the controller to use some surface mount components. This is still a prototype and the final version will have all surface mount components and be a bit smaller. I also ported the code from MBasic to PicBasic Pro. MBasic is a great program but the makers have not updated it to include newer PICs. As such, I've been using PicBasic Pro which is a really nice basic compiler. The code size and speed rivals that of some PIC-C compilers.
Schematic
Newest Schematic with fix for connection to PC or microcontroller
Better view of the schematic can be downloaded at the following link: http://picasaweb.google.com/lh/photo/0gbrdTCrjH6KJyib-i33EQ?feat=directlink
Old schematic with flaw. Recommend not to build from this schematic
Better view of the schematic can be downloaded at the following link: http://picasaweb.google.com/lh/photo/Yi30Oi9tf_1AIOc2Z4cDGw?feat=directlink
Better view of the schematic can be downloaded at the following link: http://picasaweb.google.com/lh/photo/ySbtGz3Fb4xDZ26780GD8w?feat=directlink
Netlist:
| Hobbybotics LCD Controller V2.3 | ||||
| Component | Description | Part Number | Vendor | Cost |
| C1 | 0.1uf, SMT 0805 | 80-C0805C104M5R | Mouser | $0.05 |
| D1 | 1N4148, D0-35 | 512-1N4148T26A | Mouser | $0.03 |
| J1 | 8-Pin Straight Header, Male | 855-M20-9730846 | Mouser | $0.20 |
| J2 | 6-Pin Receptacle, Female | 649-68685-306LF | Mouser | $1.75 |
| J3 | 6-Pin Receptacle, Female | 649-68685-306LF | Mouser | $1.75 |
| J4 | 6-Pin Polarized Header | 571-6404546 | Mouser | $0.27 |
| JP1 | 2-Pin Jumper | 855-M22-1920005 | Mouser | $0.25 |
| Q1 | 2N2222, SOT-23 | 512-MMBT2222AD87Z | Mouser | $0.06 |
| Q2 | 2N2222, SOT-23 | 512-MMBT2222AD87Z | Mouser | $0.06 |
| R1 | 1M, 0805, 1/8W | 71-CRCW0805J-1M-E3 | Mouser | $0.07 |
| R2 | 10k, 0805, 1/8W | 71-CRCW0805-10K-E3 | Mouser | $0.05 |
| R3 | 1k, 0805, 1/8W | 660-RK73B2ATTDD102J | Mouser | $0.06 |
| R4 | 22k, 0805, 1/8W | 71-CRCW0805-22K-E3 | Mouser | $0.05 |
| R5 | 15, 0805, 1/8W | 71-CRCW0805-15-E3 | Mouser | $0.05 |
| R6 | 10k, Potentiometer | 72-T70YE-10K | Mouser | $0.74 |
| R7 | 1k, 0805, 1/8W | 660-RK73B2ATTDD102J | Mouser | $0.06 |
| R8 | 10k, 0805, 1/8W | 71-CRCW0805-10K-E3 | Mouser | $0.05 |
| SW1 | DIP-2 Switch | 611-SDA02H1BD | Mouser | $0.56 |
| U1 | PIC16F628A, SOIC-18 | 579-PIC16F628A-I/SO | Mouser | $2.14 |
| X1 | 20Mhz Resonator | 815-AWCR-20.00MD | Mouser | $0.32 |
| HD44780 20X4 LCD | RT204-1 | Ebay | $10.80 | |
| PCB | Printed Circuit Board | HBLCD-V2.2 | ExpressPCB | $14.14 |
| Total | ||||
| $33.51 | ||||
@ Sat, 2011-04-09 23:06
i got invalid data in file
i got invalid data in file using eagle when i tried to open the regulation board schematic.
@ Sun, 2011-04-10 01:00
That's because the PCB and
That's because the PCB and schematic was done with ExpressPCB and not eagle. The application is free to use and pretty easy however, you have to use their service if you want to have PCBs made. I do use Eagle but the layout design breaks so many GUI ease of use rules that I can't bring myself to use it. Let me know if you have any further questions. \o/
@ Tue, 2010-01-12 15:42
Hi, Curtis great work !I
Hi, Curtis
great work !
I tried to program a 16F628A with your file "LCD - PIC16F628A_2Line". Everything seems OK but I have only one line on my LCD (2lines, 16 characters)
I tried with another PIC, same result ! Only the first line is working.
I tried your program "Hobbybotics LCD Controller Demo v2.2". It's working without problem, but only the first line is OK.
The second line doen't show anything.
So I tried a 4 line LCD with the file "LCD - PIC16F628A_4Line". Surprise ! Only the first and the third lines are working. Nothing appears on the second and the fourth lines ...
I don't understand where the problem is coming from... Could you help me ? Or just show me an error I could have done ?
Happy new year !
Draknaut
@ Sun, 2009-10-11 10:17
Just want to say this is a
Just want to say this is a wonderful project, Curtis.
You really have set the standard for how to document and share projects! Thanks!
@ Sun, 2009-10-11 17:05
Thanks for the kind words.
Thanks for the kind words. I believe that knowledge gained should be knowledge shared.
@ Sat, 2009-10-10 16:29
A couple questions:1. How
A couple questions:
1. How are you connecting the GPS device to the LCD controller?
2. Is the GPS device connected to its own PIC and you are sending serial strings from that to the LCD controller?
3. If you are connecting as described in step 2, did you set the LCD controller jumper to "/I"? That means you will send data to the LCD controller non-inverted. When the controller is connected to the PC data gets sent to it inverted so, the jumper has to be set to "I".
Answer those questions for me and I believe I can help you out. Posting a link to a video of what you described above would help a bit also. Your controller layout looks great also.
@ Sat, 2009-10-10 19:23
Answers!!
Hi Curtis Brooks!!
Please see my answers below!! Please advice!!
1.) The GPS Module has a Serial IO pin!! through which we can send commands to the Module requesting for the required data!! which we can be received in the same IO pin!! The datasheet for the module : http://www.parallax.com/Portals/0/Downloads/docs/prod/acc/GPSManualV1.1.pdf
The data from the microcontroller is parsed and sent to the Serial LCD at a Baud Rate of 9600 as per the below link
http://www.highonsolder.com/blog/category/gps
I've mentioned the link of the schematics diagram in my earlier post which I had posted some minutes back!!
2.) The GPS Module as such has an on-board microcontroller Basic Stamp!! Apart from that!! there is another external PIC16F84A to parse the data and send it to a Serial LCD!! The External Microcontroller is programmed with http://www.highonsolder.com/storage/code/GPS3.BAS
3.) Yes!! I've bypassed the transistor inverter!! and connected the output of the PIC16F84A to the input of the Serial LCD!! such that the Serial LCD receives only non-inverted data!!
Please do let me know if there is any shortcoming or deficit in my answers!!
I'm attaching a video of the LCD text scrolling "Searching for Satellites..."!! The video is only a 3GP!! from a mobile phone!! I've changed the extension of the file to .avi (LCD_GPS.avi) as it would'nt allow me to upload a 3GP format!! The quality is not that good!! I've not connected the GPS Module as it captured the video inside my home!! Please let me know if it is OK!! or else I'll shoot it with a digital Camera!!
Once all the hardware gets fixed!! I'll make a PCB and post it as a complete GPS Module!!
Can you please help me to modify the codes!! Please advice!!
You're help is very much appreciated :-)
Thanks and Regards,
elektor_1234
@ Sun, 2009-10-11 04:36
Believe I got it working
I believe I have it all worked out. The fix was two fold with the first being a lot of changes to the original GPS code you posted to align with the LCD controller command set. The second I have to thank you for as it helped to expose a small flaw in the controller schematic. If you look at the schematic closer than I apparently did, you would notice that when you set the jumper to non-inverted so you can connect to a microcontroller for serial control it will not work. The reason is in the way I designed the circuit for both inverted/non-inverted RS232 control. Looking at the transistor in the circuit, the collector is held high through a 10K resistor. The collector feeds to the Rx pin on the PIC. When you set the jumper to non-inverted and attempt to send data to the PIC it won't work because the line is always tied high through R8 to 5V.
There is a fix and I have included it in the archive file below. There are two ways to do this:
1. If your board is already built and your intentions are to only use this LCD in a finished design and not attached to the computer then, snip the connection from R8 to 5V and the controller will only work in the non-inverted configuration.
2. Look at the included schematic in the archive and add the shown J2 jumper to your design which will allow you to select between the two types of communication.
GPS PicBasic Pro code and schematic
My intentions are to redesign the controller a bit and this is a good catch before I made the mistake again.
I believe the mistake went unnoticed because I original wrote the code with MBasic from Basic Micro and the controller worked as expected.
Test the code out and let me know if it works for you. Be sure to make the changes I suggested above. Once I know it works as expected I'll clean the code up a bit more and add some more goodies to the GPS routines. Again, I don't have a Parallax GPS so, I can't test with that. I sent some dummy strings to it and it worked for me.
@ Sun, 2009-10-11 09:41
I'll check it out and let you know!!
Hi Curtis Brooks!!
Thanks for the updated schematics and code!! I'll program the PIC and test it and let you know the results with pictures!!
Thanks and Regards,
elektor_1234
@ Sun, 2009-10-11 14:25
GPS Results!!
Hi Curtis Brooks!!
I programmed the PIC16F84A with the code that you had posted!! Please see the results observed below!!
1.) The text scrolling stopped and the "Searching for Satellites..." and the "Error : GPS Receiver Module" Strings are now displayed properly!!
2.) I connected the GPS Module to the PIC16F84A's designated I/O port pin!! and placed the GPS Module out in the open sky!! The GPS module got a lock-on to 3+ satellites and got a fix!! But!! I do not see the co-ordinates (Lat and Long) on the LCD!! Instead!! it displays the "Error : GPS Receiver Module" string!! Not Sure why!!
I'm not sure if the GPS module receives the commands from the microcontroller and responds back!! But!! the module is functioning well!!
Can you please help me on this!! Please advice!!
Thanks and Regards,
elektor_1234