Lattice Semiconductor iCE40 UltraLite User Manual page 11

GUI Serial Communication Interface
LED Control via SPI
The Software GUI demonstration program communicates with the iCE40 UltraLite device using a SPI serial com-
munication channel. The SPI interface (mode 0) control link is implemented using a simple write-only protocol (see
Figure 10).
Figure 10. SPI Physical Transaction
CSn
SCK
MOSI
SPI Protocol
Data on the MOSI serial line is transmitted MSB first.
Addr[7:0] – Controls which of the 16 bits are updated with REG data.
Note: Unspecified REG bits must be written, but are ignored.
Addr
0x13
0x14
0x15
0x16
0x19
REG[15:0] – Consists of four control fields.
Field
aaaa
bbbb
cccc
dddd
ADDR [7:0] REG [15:8]
Bits Written
REG[3:0]
REG[7:4]
REG[11:8]
REG[15:12]
REG[15:0]
Bit Positions
REG[15:12]
REG[11:8]
REG[7:4]
REG[3:0]
iCE40 UltraLite Breakout Board
REG [7:0]
11
Bit Position
------------dddd
--------cccc----
----bbbb--------
aaaa------------
aaaabbbbccccdddd
Function
RGB Color[3:0]
Brightness[3:0]
Breathe Ramp [3:0]
Blink Rate [3:0]