HCMS2975 LED alphanumeric display

Alphanumeric LED display, 8 digits, 5x7 LED pattern. The device has an SPI interface. The library methods are similar to those used for the TextLCD library (eg locate(), cls(), printf(), putc() etc). The library supports multiple devices connected in a daisy chain. This provides a 8x1, 8x2, 16x1 and 16x2 display configuration. In daisy chain configuration the Din pin of the lower right device is connected directly to mbed, the Dout of this device is wired to its left neighbour etc. All other pins (VCC, GND, SCLK, CS, RS, RST) are wired in parallel.

These displays are from mid 80s to mid 90s and they look cool, but they are rather expensive ($100 a piece..). The lib was developed and tested with displays salvaged from some equipment. You see them mostly in HP printers, medical equipment etc. The displays are available in multiple colours (bright red, red, green, yellow, orange) and in different sizes. Type numbers are HCMS29xx.

Here is a picture of 4 red displays in 16x2 mode at 15% brightness in low light to better show the characters.

Some info can be found here and here.