This is a quick and dirty library providing a relatively easy-to-use interface for driving the Holtek HT16K33 16×8 LED driver IC.

The API commands are, in no particular order:

init(uint8_t i2c_addr)

specifies the I2C address of the IC

setBrightness(uint8_t b)

sets the brightness of the display (0–15)

setBlink(uint8_t)

sets the blink rate of the display (see note below)

resetOrientation()

resets the orientation of the display to the defaults

reverse()

reverses the order of the two 8×8 sub-matrices (again, see note below)

flipVertical()

flips the matrix data vertically before writing to the IC

flipHorizontal()

flips the matrix data horizontally before writing to the IC

clear()

clears the matrix completely†

setPixel(uint8_t row, uint8_t col, uint8_t onoff)

sets the state of a single pixel. onoff should be either 0 (off) or 1 (on)†

setRow(uint8_t row, uint16_t value)

sets the content of an entire row (16 bits)†

getRow(uint8_t row)

gets the content of an entire row (16 bits)†

setColumn(uint8_t col, uint8_t value)

sets the content of an entire column (8 bits)†

write()

writes the display buffer to the IC (updates the display)

† note: none of these will write anything to the IC—you will still need to call write().

For various reasons, blink rates are #define-d as a set of constants:

HT16K33_BLINK_OFF

disable blinking (default)

HT16K33_BLINK_1HZ

set blink rate to 1Hz

HT16K33_BLINK_2HZ

set blink rate to 2Hz

HT16K33_BLINK_0HZ5

set blink rate to 0.5Hz

This only really makes sense if you’re using a 16×8 matrix made of two discrete 8×8 matrixes. If you’re rolling it yourself or using a single 16×8, you may as well ignore this section.

This library assumes that, if you’re using two 8×8 matrixes, you’ve wired them correctly with ROW0 on the left-hand edge of the left-most matrix, and ROW15 on the right-most edge, thus:

 0      7 8     15
+--------+--------+
|        |        |
|        |        |
|        |        |
+--------+--------+

However, just occasionally your concentration will slip and you’ll end up with something like this:

 8     15 0      7
+--------+--------+
|        |        |
|        |        |
|        |        |
+--------+--------+

Rather than having to rewire everything/rework your PCBs, you can just call reverse(), and the library will cover for you…
(no, this didn’t happen to me. I don’t know why you would think that /s)