GLO-216Y/G Programmer's Reference

This page describes the GLO-216's fonts and instruction set. For hookup, configuration and specifications, please see the hardware reference.

Table of Contents

Programming	Other Pages
Serial Communication	Index, Revision History
Character Set	Hardware Reference
Screen Layouts	BPI/BPK Compatibility
Control Codes	Product Description
Escape Instructions

Serial Communication

GLO-216s accept asynchronous serial at 9600bps, 8 data bits, no parity, 1 or more stop bit(s), often called "N81." They will accept RS-232 input, inverted TTL, or non-inverted TTL. Non-inverted TTL requires cutting the SPol jumper on the circuit board. See the hardware reference for further information.

Character Set

GLO-216s display the standard ASCII character set for character codes 32 to 127 (0x20-0x7F hex). Character codes 128-143 (0x80-0x8F hex), the last row in the chart below, are custom characters that can redefined and saved to EEPROM using Escape instructions.

Character Set (Character code= row+column)
Last row, 128-143, is the default custom-character set.

Screen Layouts

GLO-216 offers four font sizes, which can be freely mixed on the screen. The following screen layouts show position values for the various font sizes. Positioning (ctrl-P below) is in terms of the font-size in effect at the time.

Default 2x16 Screen Layout
Position=row+column.

Tall-character, 1x16 Screen Layout

Wide-character, 2x8 Screen Layout
Position=row+column.

Large-character, 1x8 Screen Layout
(7-segment numbers)

Large-character, 1x8 Screen Layout
(text-style numbers)

Control Codes

GLO-216s understand a small set of control codes modeled on those used by our BPP, VFD, ILM, TRM and SGX products, but with OLED-specific tweaks. Here's a list of quick descriptions. Codes not listed below (e.g., Null, 0) are ignored by the display.

Items marked with » can be clicked for tips or more detail.

Home (ctrl-A) 01 dec 0x01 hex

Moves the printing position to 0, the first character of the top line. »

For example, you clear the screen and send the text Hello— Hello appears at the upper left of the screen, in positions 0-4. Now you send ctrl-A, followed by J— Hello becomes Jello.

Select Font Size (ctrl-B) 02 dec 0x02 hex

Cycles the font size, normal→tall→wide→big→normal... »

When you send ctrl-B, text already on the screen is unaffected; the instruction tells the display to change the font size of any subsequent text. Although the font-size selections wrap around, it's easy to lose track when programming, so it's smart to send ctrl-C to set the font size to normal, then the desired number of ctrl-B characters to get the font size you want.

Set Font Size to Normal (ctrl-C) 03 dec 0x03 hex

Sets the font to the default, small size (two lines of 16 characters. »

Rather than continuously cycling through the font-size choices, it's usually better to send ctrl-C to set the normal size, then send ctrl-Bs as necessary to select the desired size.

Backspace (ctrl-H) 08 dec 0x08 hex

Backs up one character, erases that character, sets the print position to erased character's location. »

Behaves exactly like the Backspace key.

Tab (ctrl-I) 09 dec 0x09 hex

Moves the printing position to the next multiple-of-4 screen location: 0→4→8→12→16→20→24→28→0... »

While it's normally better to use the ctrl-P position instruction, using tab to move around the screen may sometimes be convenient. Tabs always fall in the same screen locations regardless of the font size in effect at the time.

Smart Linefeed (ctrl-J) 10 dec 0x0A hex

Moves the printing position down a line. »

If the printing position is on the first line, ctrl-J moves it to the second line; if it's on the second, it wraps back to the first line. If the display receives a carriage return/linefeed combination, it ignores the linefeed; that's what makes it "smart."

Vertical Tab (ctrl-K) 11 dec 0x0B hex

Moves the printing position up a line. »

On a two-line display, there's no difference between moving up a line or down one; both amount to moving to the same spot on the other line. Linefeed and Vtab are both supported for consistency with multiline displays.

Clear Screen (ctrl-L) 12 dec 0x0C hex

Clears the screen and moves the printing position to 0—the first position of the first line. »

Use clear-screen sparingly. If you need to update a few characters on the screen, move to that position (using ctrl-P below) and print over the old characters. To update the entire screen, send Home (ctrl-A) and replace the screen contents with 32 brand-new characters (assuming default font). Clearing the screen unnecessarily causes an annoying blink effect.

Carriage Return (ctrl-M) 13 dec 0x0D hex

Moves to the first printing position of the next line. »

Same effect as a Home (ctrl-A) plus a linefeed (ctrl-J). Linefeeds paired with carriage returns are ignored.

Turn On OLED driver (ctrl-N) 14 dec 0x0E hex

Turns on the OLED driver circuitry after a previous ctrl-O turned it off. »

The OLED drivers can be turned off to save power using ctrl-O; this instruction turns them back on. Data displayed when ctrl-O occurred will be restored. By default, the screen is on, so this instruction is only needed to undo the effects of a previous ctrl-O.

Turn Off OLED driver (ctrl-O) 15 dec 0x0F hex

Turns off the OLED driver circuitry to save power. »

Ctrl-O will blank the screen and reduce current draw to about 5mA. When the screen is off, the control electronics remain on, so the unit continues to receive and process text and instructions. Any changes will be visible when the OLED drivers are turned back on.

Set Printing Position (ctrl-P) 16 dec 0x10 hex

Sets the printing position according to the value of the next byte, position+64 (0x40 hex). »

Screen positions are in terms of the font size in effect at the time, so the range is 0-31 for the 2x16 font and 0-7 for the big, 1x8 font. It's not recommended for programming purposes, but you can also use a text number like "24" to specify ctrl-P position values. Text numbers must be followed by a throwaway character—like a space or a period—which will terminate the number but won't be displayed.

Right-align Text (ctrl-R) 18 dec 0x12 hex

Displays text (usually numeric) within a field 2 to 8 characters wide. The byte that follows ctrl-R is a text number from '2' to '8' (50-56 dec, 0x32-0x38 hex) that sets the field width. The text after that will be invisibly stored until one of the following is received:

• A control code.
• A period/decimal point.
• The specified number of bytes.

When this happens, the field will be cleared and the received text printed at the righthand end of the field. »

Right align works backward from the printing position in effect at the time. Make sure that there's enough space behind the printing position to avoid breaking the right-aligned text across lines.

Set 7-Segment Big Numbers (ctrl-S) 19 dec 0x13 hex

Sets 7-segment-style bitmaps for numbers displayed at the largest font size (default).»

The standard font consists of the usual 5x7-pixel patterns. This leaves a pixel-width space between characters both horizontally and vertically. When this font is scaled up to make double-sized characters, two pixels of potential height are lost. To make the big numbers as BIG as possible, GLOs have an extra 5x8 number font used in the big (1x8) character mode.

Set Text-style Big Numbers (ctrl-T) 20 dec 0x14 hex

Sets normal text patterns for numbers displayed at the largest font size.»

GLO normally uses the larger, 7-segment font to print numbers in its largest (1x8) mode. If you prefer the bitmaps used at smaller sizes, use this instruction.

Escape: Start Multipart Instruction (ctrl-[) 27 dec 0x1B hex

See the Escape-code descriptions below.

BPI/BPK Instruction Prefix (NA) 254 dec 0xFE hex

See BPI Upgrade Guide.

Escape Instructions

These are multipart instructions that begin with the Escape character; 27 dec, 0x1B hex. Escape instructions affect memory: writing bitmaps to RAM to define custom characters, or storing/recalling text or character patterns to/from EEPROM.

Define Custom Character Pattern ESC D n B0 B1 B2 B3 B4 B5 B6 B7

Change the pattern of custom character n to the bitmap made up of bytes B0 through B7. The value n is a text number '0' to '7' (48-55 dec, 0x30-0x37 hex) specifying the custom character to be defined.

The figure below shows how the bits of bytes B0 through B7 define the shape of the custom character. The upper three bits of the pattern bytes are ignored. A tool for calculating custom-character bytes is online at seetron.com.

Bitmap Layout for Custom Characters.

GLO-216 supports 16 custom characters, double the 8 allowed by LCDs. To maintain backward compatibility, the lower 8 characters are defined by ESC D (uppercase D; 68 dec, 0x44 hex) and the upper set by ESC d (lowercase d; 100 dec, 0x64 hex). The custom characters map to character codes 128-143 dec (0x80-0x8F hex) as shown in the character chart above.

An example: To define custom-character 3 (which maps to character code 131) to the °F pattern in the example above, you'd send the sequence of 11 bytes shown below. To define custom character 10 (maps to char code 138) instead, you would substitute 100 dec/0x64 hex (lowercase d) for 68 dec/0x44 hex (uppercase D).

	ESC	D	'3'	B0	B1	B2	B3	B4	B5	B6	B7
Dec:	27	68	51	8	20	8	7	4	6	4	4
Hex:	0x1B	0x44	0x33	0x08	0x14	0x08	0x07	0x04	0x06	0x04	0x04

Custom Characters: GLO versus LCD

GLO-216 allows redefinition of custom characters without altering custom characters already on the screen. This is a significant change from LCD custom-character behavior. »

LCDs custom-character patterns are stored in a patch of RAM on the LCD. This is why the LCD's eight-character limit cannot be overcome; it's set in hardware. Sooner or later programmers try reusing characters; they print custom character 0, redefine it, and print it again, expecting two different patterns on the LCD. To their consternation, both the old and new characters adopt the new bit pattern. GLO-216's custom-character RAM is in the serial interface, so it is possible to reuse characters. There's no technical reason to stop you from printing a character, redefining it, printing, redefining...across the entire screen. So the custom-character capacity is essentially unlimited; if 16 is still not enough, you can recycle previously used characters.

Recall Saved Data (text or custom characters) from EEPROM ESC E 0

Recall stored data from EEPROM. ESC E (uppercase E; 69 dec, 0x45 hex) 0 (zero; 48 dec, 0x30 hex) recalls the saved startup text to the screen. The same instruction with lowercase e (101 dec, 0x65 hex) recalls the saved custom-character set from EEPROM (without affecting the screen). »

Changes made to custom characters using ESC-D are written to RAM and are lost when the power is turned off. They can be saved to EEPROM using ESC x 0. ESC e 0 recalls the custom characters stored in EEPROM and transfers them to RAM, undoing all redefinitions. This has no effect on the current contents of the screen.

Store Data (text or custom characters) to EEPROM ESC X 0

Store data to EEPROM. ESC X (uppercase X; 88 dec, 0x58 hex) 0 (zero; 48 dec, 0x30 hex) saves all text and instructions received since the last ctrl-L clear-screen. The same instruction with lowercase x (120 dec, 0x78 hex) saves the current custom-character set.

These instructions can be disabled in order to protect the data from accidental changes by cutting the DSU (display setup) jumper on the interface pcb.

Additional Info on ESC X 0 (Store Text)

The basic purpose of ESC X 0 is to store a string of text that will be used at startup to display a splash screen, like the default model/version screen. But ESC X 0 can store instructions too, up to a total of 48 bytes. The only instruction it will not store is clear-screen, which it uses as a start marker. Why allow embedded instructions? It lets you set defaults (e.g., font size, or initial printing position) that will be in effect as soon as the display powers up, or anytime an ESC E 0 is sent.

The flexible nature of this mechanism means that you may get unexpected results when you recall the stored text/data; for example, if the screen is not cleared beforehand, or if a different font size is in effect.