Wednesday, October 16, 2013

Noritake Itron GU256X64-901A VFD(Vacuum Fluorescent Display)

Digital Thermometer vs. NTC thermistors


Why VFD (Vacuum fluorescent Display)?

Compared to LED, VFD (Vacuum Fluorescent Display) is compact and light weighted, has excellent readability with a wide viewing angle, high reliability and long life span. VFD is a self-illuminating display with high brightness and visibility whereas LCD can be seen only when there are added backlight since it does not emit backlight itself. VFD also has higher color representation, better graphic display quality than LED

That's the why.



A few month ago, i got a Vacuum-Fluorescent-Display (VFD),  Unfortunately No longer display the data
GU256X64-901A

GU256X64-901A 256 x 64 Dot Graphic VFD
Operating Temp -40°C to +85°C
Single 5V Supply.
High Brightness Blue Green Display
8 bit High Speed Parallel Interface
ASCII + Extended Character Font
Twin Graphic/Character RAM
4 Level Brightness Control Function

ELECTRICAL SPECIFICATION
Parameter Symbol Value Condition
Power Supply Voltage VCC 5.0VDC +/- 5% GND=0V
Power Supply Current ICC 1.4ADC typ. Vcc=5V
Logic High Input VIH 3.5VDC min. -
Logic Low Input VIL 1.5VDC max. -
Logic High Output VOH 4.0VDC min. IOH = -2mA
Logic Low Output VOL 0.4VDC max. IOL =4mA
The power on rise time should be less than 100ms.The inrush current at power on can be 2 x ICC






Some repair by the former owner, Missing Inductor, Damage PCB Trace, Crushed Capacitor
Are you all right?













Fuse OK, Soldered the damage trace and missing part back together(temporarily)
Fix Inductor, 47uH,DC Resistance Max : 0.079Ω, RMS Current (Irms) : 3.7A
after completing repairs

Self Test(Top Left Coner Pin 1,2 Short), 
VFD phosphors will burn in with repetitive images.
shows common legends from the convenience store Warning mesage
"19세 미만의 청소년에게는 술, 담배를 판매하지 않습니다" 
"We don't sell drink and cigarette for under 19"

Stil Alive! anyway.
Self Test(Top Left Coner Pin 1,2 Short)

Voilà!









Color filters(Smoke, Orange, Red)



Caveats: 
1. Font data to interface with a serial EEPROM using the I2C, refer to font.h
2. VFD module has Pixel orientation per Byte: D7..D0 (MSB First) characteristics,
refer to font.c

fonts.h
If you dont want Serial EEPROM, Modify fonts.h (see below, read comment)
#define FONT_EXTERNAL_EEPROM      1  // 1:External EEPROM,0:Internal Flash
#define FONT_HANGUL               1  // 1:Hangul are used in this program
/*
 * Internall Flash memory
 * Select desired fonts. (Simply comment out those not needed)
*/
/////#define FONT_ARIAL_NARROW_8_X12        
#define FONT_ARIAL_NARROW_9_X12B
/////#define FONT_ARIAL_NARROW_12_X16
/////#define FONT_ARIAL_NARROW_13_X16B
/////#define FONT_ARIAL_NARROW_18_X23B

font.c
static uint8_t _reverse_bits(uint8_t data)
/*
 * Reverse Bits of a byte
 *
 * Why reverse bits?
 *
 * I do not create work, use existing Column Major Font Data.
 * SAMSUNG KS0108 is a representative Controller of the Column Major
 * And Pixel orientation per Byte: D0..D7 (LSB First) characteristics.
 * LSB First rules generally apply to Column Major Coltroller
 * But Noritake VFD is D7..D0(MSB First) that is the reverse (Futaba Dot Matrix VFD are the same)
 *
 * That's the why.
 *
 * Column Major Display Pixel orientation per Byte (from top to bottom)
 *
 *      row             most cases   Noritake,Futaba
 *       0                 0               7
 *       1                 1               6
 *       2                 2               5
 *       3                 3               4
 *       4                 4               3
 *       5                 5               2
 *       6                 6               1
 *       7                 7               0
 *       8                 0               7
 *       9                 1               6
 *      10                 2               5
 *       .                 .               .
 *       .                 .               .
 *       .                 .               .
 *      64                 7               0
 *
 * Time Complexity: O(log n)
 *
 * O(n log n) is better performace but i cannot found googgle
 * http://www-graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
 *
 */


Useful Links
in 1967, He is the inventor of a Vacuum fluorescent display called the VFD
has passed away on March 25, 2013.