USB and serial enabled LCD backpack design overview
From DP
| USB and serial enabled LCD backpack design overview | |
|---|---|
| Codename | PIC LCD backpack |
| Status | Test production |
| Development | development forum |
| ID # | {{{id}}} |
Prototype PCBs are available in the free PCB drawer.
This is a USB and serial backpack for simple HD44780 character LCD screens. It has a few nice features that set it apart from the serial-only LCD backpacks at SparkFun and Adafruit:
- USB and serial control of characters LCDs
- Supported in common software (LCD Smartie) as 'matrix orbital' display
- Adjust contrast and backlight from software
- Couple extra pins for buttons
- 500mA fuse
- USB upgradable
We like this project, but we probably won't produce it because HD44780 LCDs aren't very popular anymore. If you'd like a PCB (and plan to build it) please let us know in the comments.
Contents |
Overview
History and related links
Prototypes
Hardware
Click for a full size schematic image. Schematic and PCB were designed with the freeware version of Cadsoft Eagle, download the latest project files from our Google Code project page.
Microcontroller section
- Microcontroller
- Power and decoupling
- Oscillator
- Programming and reset support
- LEDs
Another part of it
PCB
We used the freeware version of Cadsoft Eagle to make the schematic and PCB. Download the latest designs and firmware from the project Google Code page.
- PCB and placement notes
- soldering advise
Partslist
| Part | Quantity | Value | Package |
|---|---|---|---|
| BACKLIGHT | 1 | 100R | B25P |
| C1,C2 | 2 | 27pf | C0805 |
| C3 | 1 | 220nF | C0805 |
| C4 | 1 | 0.1uF | C0805 |
| CONTRAST | 1 | 10K | B25P |
| D1 | 1 | BAS16J | SOD2514X100N |
| F1 | 1 | 500mA | RCL_L1812 |
| IC1 | 1 | PIC18F2550_28W | SO28W |
| ICSP | 1 | 1X05 | |
| J1 | 1 | USBSMD | USB-MINIB |
| LCD | 1 | 1X16 | |
| Q1 | 1 | 20MHz | HC49UP |
| R1 | 1 | 10k | R0805 |
| R2 | 1 | 1K | M0805 |
| RB4,RB5 | 2 | 1X01 | |
| SJ1 | 1 | SJ_2 | |
| T1 | 1 | BC818 | SOT23-BEC |
| UART,USB | 2 | 1X04 |
The latest sources and distributors are in the master partlist. See something missing? Please let us know.
Firmware
The firmware is written in C and compiled with the free Microchip C18 compiler. You can download the latest files from our Google Code project page.
- Operating modes
- extra software required
We used the Microchip USB stack to run the 18F2550 as a virtual serial port. Microchip's code is open but not redistributable. If you want to compile the source, download the stack from Microchip, then drag the source code into the install directory. See the detailed instructions in the PIC compiler how-to.
.inf installation
The virtual serial port (CDC) is an open standard, it should work on any modern operating system.
You don't need a driver, but you will need a .inf file to tell Windows how to use the device. A suitable .inf is included in the project archive.
Commands
The controller implements a (subset) of the serial interface provided by Matrix Orbital Serial LCDs.
To send a command, first send the START_COMMAND byte (0xFE), followed by the command (with any parameters), followed by the END_COMMAND byte (0x9A).
For example, to turn on the backlight, send 0xFE, 0x42, 0x00, 0x9A.
| Name | Decimal | Hex | Parameters |
|---|---|---|---|
| MATRIX_ORBITAL_COMMAND | 254 | 0xFE | None |
| BACKLIGHT_ON | 66 | 0x42 | 1 (minutes, 00=forever) |
| BACKLIGHT_OFF | 70 | 0x46 | None |
| CLEAR | 88 | 0x58 | None |
| HOME | 72 | 0x48 | None |
| POSITION | 71 | 0x47 | 2 (col, row) |
| UNDERLINE_CURSOR_ON | 74 | 0x4A | None |
| UNDERLINE_CURSOR_OFF | 75 | 0x4B | None |
| BLOCK_CURSOR_ON | 83 | 0x53 | None |
| BLOCK_CURSOR_OFF | 84 | 0x54 | None |
| BACKLIGHT_BRIGHTNESS | 152 | 0x98 | 1 (brightness) |
| CUSTOM_CHARACTER | 78 | 0x4E | 9 (character #, 8-byte bitmap) |
| NETWORK_CONFIG | 153 | 0x99 | None |
| END_COMMAND | 154 | 0x9A | None |
Bootloader
Source and license
Taking it further
Here's some ideas for the future:
- List
We'll post the most recent firmware updates on our blog. You can also join the discussion in the [forum].
Get one!
You can [get one for $00], including worldwide shipping.
Your purchases at Seeed Studio keep the open source project coming, we sincerely appreciate your support!