iCESugar-pro 是基于Lattice LFE5U-25F设计的一款开源FPGA开发板，板载32MB SDRAM，32MB SPI-Flash，支持启动RISC-V Linux，板载iCELink调试器经过精心设计，支持拖拽烧录，调试串口，以及双JTAG接口，只需一根TYPE-C线即可进行开发测试，开发板使用DDR SODIMM 接口引出106个可用IO，可配合底板进行扩展测试。
这应该是这个系列的最后一款开发板了，使用Lattice ECP5系列FPGA，这个系列的功能性能要比先前的ice40系列强很多（实测可以跑198MHz的RISC-V）单板规格如下：
ECP5
LFE5U-25F-6BG256C (24K LUT)
SDRAM
IS42S16160B (32MB)
SPI-Flash
W25Q256JV (32MB)
Clock
25MHz 外部时钟
使用DDR SODIMM接口引出了 106个GPIO（就是树莓派 CM3的金手指接口），可以自行设计底板使用，QQ群内也有群主设计的底板原理图和PCB，可以自行打样。
运行linux基于vexriscv，使用了litex框架（一个法国的团队基于nmigen实现的），具体可以参考github，有更详细的介绍。
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Build your hardware, easily!
(c) Copyright 2012-2020 Enjoy-Digital
(c) Copyright 2007-2015 M-Labs
BIOS built on Nov 11 2020 09:43:40
BIOS CRC passed (9f19f473)
Migen git sha1: cc6e76e
LiteX git sha1: 275932f5
--=============== SoC ==================--
CPU: VexRiscv_Linux @ 50MHz
BUS: WISHBONE 32-bit @ 4GiB
CSR: 8-bit data
ROM: 64KiB
SRAM: 8KiB
L2: 8KiB
SDRAM: 32768KiB 16-bit @ 50MT/s (CL-2 CWL-2)
--========== Initialization ============--
Initializing SDRAM @0x40000000...
Switching SDRAM to software control.
Switching SDRAM to hardware control.
Memtest at 0x40000000 (2MiB)...
Write: 0x40000000-0x40200000 2MiB
Read: 0x40000000-0x40200000 2MiB
Memtest OK
Memspeed at 0x40000000 (2MiB)...
Write speed: 11MiB/s
Read speed: 10MiB/s
--============== Boot ==================--
Booting from serial...
Press Q or ESC to abort boot completely.
sL5DdSMmkekro
Timeout
Booting from SDCard in SPI-Mode...
Booting from boot.json...
Copying Image to 0x40000000 (4545524 bytes)...
[########################################]
Copying rootfs.cpio to 0x40800000 (8029184 bytes)...
[########################################]
Copying rv32.dtb to 0x41000000 (1987 bytes)...
[########################################]
Copying emulator.bin to 0x41100000 (9600 bytes)...
[########################################]
Executing booted program at 0x41100000
--============= Liftoff! ===============--
VexRiscv Machine Mode software built Mar 23 2020 16:55:03
--========== Booting Linux =============--
[ 0.000000] No DTB passed to the kernel
[ 0.000000] Linux version 5.0.13 (florent@lab) (gcc version 8.3.0 (Buildroot 2019.08-rc2-00011-gad9efda578)) #1 Thu Sep 12 14:20:26 CEST 2019
[ 0.000000] earlycon: sbi0 at I/O port 0x0 (options '')
[ 0.000000] printk: bootconsole [sbi0] enabled
[ 0.000000] Initial ramdisk at: 0x(ptrval) (8388608 bytes)
[ 0.000000] Zone ranges:
[ 0.000000] Normal [mem 0x0000000040000000-0x0000000041ffffff]
[ 0.000000] Movable zone start for each node
[ 0.000000] Early memory node ranges
[ 0.000000] node 0: [mem 0x0000000040000000-0x0000000041ffffff]
[ 0.000000] Initmem setup node 0 [mem 0x0000000040000000-0x0000000041ffffff]
[ 0.000000] elf_hwcap is 0x1101
[ 0.000000] Built 1 zonelists, mobility grouping on. Total pages: 8128
[ 0.000000] Kernel command line: mem=32M@0x40000000 rootwait console=liteuart earlycon=sbi root=/dev/ram0 init=/sbin/init swiotlb=32
[ 0.000000] Dentry cache hash table entries: 4096 (order: 2, 16384 bytes)
[ 0.000000] Inode-cache hash table entries: 2048 (order: 1, 8192 bytes)
[ 0.000000] Sorting __ex_table...
[ 0.000000] Memory: 19812K/32768K available (3415K kernel code, 148K rwdata, 509K rodata, 140K init, 216K bss, 12956K reserved, 0K cma-reserved)
[ 0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[ 0.000000] NR_IRQS: 0, nr_irqs: 0, preallocated irqs: 0
[ 0.000000] clocksource: riscv_clocksource: mask: 0xffffffffffffffff max_cycles: 0xb8812736b, max_idle_ns: 440795202655 ns
[ 0.000422] sched_clock: 64 bits at 50MHz, resolution 20ns, wraps every 4398046511100ns
[ 0.004800] Console: colour dummy device 80x25
[ 0.007486] Calibrating delay loop (skipped), value calculated using timer frequency.. 100.00 BogoMIPS (lpj=200000)
[ 0.009456] pid_max: default: 32768 minimum: 301
[ 0.026679] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.028428] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
[ 0.121644] devtmpfs: initialized
[ 0.189497] random: get_random_bytes called from setup_net+0x4c/0x188 with crng_init=0
[ 0.200282] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645041785100000 ns
[ 0.202998] futex hash table entries: 256 (order: -1, 3072 bytes)
[ 0.220630] NET: Registered protocol family 16
[ 0.579278] clocksource: Switched to clocksource riscv_clocksource
[ 1.118845] NET: Registered protocol family 2
[ 1.149705] tcp_listen_portaddr_hash hash table entries: 512 (order: 0, 4096 bytes)
[ 1.152735] TCP established hash table entries: 1024 (order: 0, 4096 bytes)
[ 1.154585] TCP bind hash table entries: 1024 (order: 0, 4096 bytes)
[ 1.156926] TCP: Hash tables configured (established 1024 bind 1024)
[ 1.164153] UDP hash table entries: 256 (order: 0, 4096 bytes)
[ 1.165932] UDP-Lite hash table entries: 256 (order: 0, 4096 bytes)
[ 1.197310] Unpacking initramfs...
[ 5.478529] Initramfs unpacking failed: junk in compressed archive
[ 5.518894] workingset: timestamp_bits=30 max_order=13 bucket_order=0
[ 6.441722] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 253)
[ 6.443061] io scheduler mq-deadline registered
[ 6.444868] io scheduler kyber registered
[ 9.806243] f0001000.serial: ttyLXU0 at MMIO 0xf0001000 (irq = 0, base_baud = 0) is a liteuart
[ 9.809098] printk: console [liteuart0] enabled
[ 9.809098] printk: console [liteuart0] enabled
[ 9.810562] printk: bootconsole [sbi0] disabled
[ 9.810562] printk: bootconsole [sbi0] disabled
[ 9.863872] libphy: Fixed MDIO Bus: probed
[ 9.874843] i2c /dev entries driver
[ 9.993741] NET: Registered protocol family 10
[ 10.037459] Segment Routing with IPv6
[ 10.042318] sit: IPv6, IPv4 and MPLS over IPv4 tunneling driver
[ 10.141414] Freeing unused kernel memory: 140K
[ 10.142302] This architecture does not have kernel memory protection.
[ 10.144239] Run /init as init process
mount: mounting tmpfs on /dev/shm failed: Invalid argument
mount: mounting tmpfs on /tmp failed: Invalid argument
mount: mounting tmpfs on /run failed: Invalid argument
Starting syslogd: OK
Starting klogd: OK
Running sysctl: OK
Initializing random number generator... [ 16.221885] random: dd: uninitialized urandom read (512 bytes read)
done.
Starting network: OK
Starting dropbear sshd: [ 19.262912] random: dropbear: uninitialized urandom read (32 bytes read)
OK
Welcome to Buildroot
buildroot login: root
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32-bit VexRiscv CPU with MMU integrated in a LiteX SoC
login[81]: root login on 'console'
root@buildroot:~# uname -a
Linux buildroot 5.0.13 #1 Thu Sep 12 14:20:26 CEST 2019 riscv32 GNU/Linux
root@buildroot:~# cat /proc/cpuinfo
processor : 0
hart : 0
isa : rv32ima
mmu : sv32
uarch : spinalhdl,vexriscv
root@buildroot:~# cat /proc/meminfo
MemTotal: 19952 kB
MemFree: 7756 kB
MemAvailable: 7208 kB
Buffers: 0 kB
Cached: 9260 kB
SwapCached: 0 kB
Active: 380 kB
Inactive: 0 kB
Active(anon): 380 kB
Inactive(anon): 0 kB
Active(file): 0 kB
Inactive(file): 0 kB
Unevictable: 9260 kB
Mlocked: 0 kB
SwapTotal: 0 kB
SwapFree: 0 kB
Dirty: 0 kB
Writeback: 0 kB
AnonPages: 408 kB
Mapped: 2236 kB
Shmem: 0 kB
KReclaimable: 584 kB
Slab: 2124 kB
SReclaimable: 584 kB
SUnreclaim: 1540 kB
KernelStack: 176 kB
PageTables: 60 kB
NFS_Unstable: 0 kB
Bounce: 0 kB
WritebackTmp: 0 kB
CommitLimit: 9976 kB
Committed_AS: 1672 kB
VmallocTotal: 524287 kB
VmallocUsed: 0 kB
VmallocChunk: 0 kB
Percpu: 32 kB
root@buildroot:~#
参考
iCESugar-pro
https://github.com/wuxx/icesugar-pro
linux-on-litex-vexriscv
https://github.com/litex-hub/linux-on-litex-vexriscv
linux-on-litex-vexriscv-prebuilt
https://github.com/antmicro/linux-on-litex-vexriscv-prebuilt