Insights

The LTC1799 specification shows that the max. freq. of 33MHz is achievable only when using 5V input and it incurs in 2.5% of variance. For 3V, the max. freq. is 20MHz. Using an oscilloscope was possible to see the generated clock signal is highly smoothed.

• This does not appear to affect the demo application included in the firmware; however, on my board, I made some changes to have it operate at 10 MHz—the maximum recommended frequency for 3V, with a maximum variation of 2% when above 25°C.

The manual says the M25P10A (on the back of the board) is suffice to hold 2 programs, making it possible to use the WarnBoot feature of the iCE40.

The demo application (Windows only) for the board can be found in the Adept 2 from Digilent, also both the programmer driver and the SDK. The version 2 works with the board.

This board isn't very popular in the FOSS community because of the reliance on the proprietary closed  ADEPT firmware in the AT90.

• There are many popular open source programmers for iCE40 boards using FTDI chips, you can use the JJP1 and J11 header for external firmware writing.

• There are two open source programmers, iceBurn and iceDude, that do not use ADEPT library but reverse engineered the USB messages.

[ToDo] I'm toying with the ADEPT2 SDK and was able to enumerate the ice40 board and its peripherals. In my tests I was able to read, clean and write to the Flash, now I need to implement the ice40 firmware protocol. The firmware in the ice40Blink exposes:

• GPIO port, with some bits for the power/reset (output) and CDONE (input)

• SPI port, for the Flash

• Parallel Port, used by the demo