Rust Hello World for the MilkV-Duo

This project aims to implement a HID on the MilkV-Duo. The MilkV-Duo doesnt have a GPU or any OpenGL/... acceleration. Cause of the lack, drawing to a screen is running 100% on the CPU not accelerated. Plus - most graphic librarys wont work without OpenGL/Vulkan/... . Thats why this project started. I wanted a way to simply directly draw to the framebuffer device without X11 or any X11 related hacks.

It uses the embedded-graphics crate - keep in mind that graphic operations are rather simple compared to software stacks like lvgl (please someone make cross compiling work for the lvgl bindings).

Background: I tryed using the SDL2 and lvgl-bindings crate - but i failed cross compiling it. If someone succeeds cross-compiling them, please create an issue in this repo or write me an email.

Sources

Based on: https://barretts.club/posts/i-got-a-milkv-duo/

Build

Just run ./compile.sh once for the initial setup and first build. The script will also install the toolchain required.

Add a display to the MilkV

Use the following source:

https://milkv.io/docs/duo/resources/spilvgl#bring-up-the-spi-display However, tho this example is made for the ST7789V - you can easilly add any by linux suported graphic display.

Heres another example: https://gist.github.com/miathedev/f5a502eec78e4bc113cdb82935824a4e

Its basically always the same. Most important part on the MilkV is patching the fbtft_request_one_gpio function.

ToDo

• Remote Debugging
• Audio
• Sprites
• MilkV Mailbox
• MilkV GPIO

Known errors/tricks

Connect to wifi

Using wpa_supplicant from the device

Source: https://community.milkv.io/t/connect-to-wi-fi-on-duo-s/1540

Start wpa_supplicant with:

echo "update_config=1" >> /etc/wpa_supplicant.conf
wpa_supplicant -B -i wlan0 -c /etc/wpa_supplicant.conf

At this point run:

wpa_cli -i wlan0

Use the scan and scan_results commands to see the available networks:

> scan
OK
<3>CTRL-EVENT-SCAN-STARTED 
<3>CTRL-EVENT-SCAN-RESULTS 
> scan_results
bssid / frequency / signal level / flags / ssid
11:22:33:44:55:66       5745    -78     [WPA2-PSK-CCMP][ESS]    MYSSID-5G
11:22:33:44:55:67       2427    -85     [WPA2-PSK-CCMP][ESS]    MYSSID
To associate with MYSSID-5G, add the network, set the credentials and enable it:

> add_network
1
> set_network 1 ssid "MYSSID-5G"  
OK
> set_network 1 psk "password"
OK
> enable_network 1

If the SSID does not have password authentication, you must explicitly configure the network as keyless by replacing the command set_network 1 psk "password" with set_network 1 key_mgmt NONE.

Finally save this network in the configuration file and quit wpa_cli:

> save_config
OK
> quit

[root@milkv-duo]~# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
    link/ether 66:69:54:69:1c:2c brd ff:ff:ff:ff:ff:ff
    inet 169.254.206.92/16 brd 169.254.255.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
3: usb0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 7e:eb:9c:48:33:3c brd ff:ff:ff:ff:ff:ff
    inet 192.168.42.1/24 brd 192.168.42.255 scope global usb0
       valid_lft forever preferred_lft forever
4: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
    link/ether 88:00:33:77:f1:0f brd ff:ff:ff:ff:ff:ff
    inet 192.168.0.175/24 brd 192.168.0.255 scope global dynamic noprefixroute wlan0
       valid_lft 84829sec preferred_lft 74029sec
[root@milkv-duo]~# ping baidu.com
PING baidu.com (39.156.66.10): 56 data bytes
64 bytes from 39.156.66.10: seq=0 ttl=49 time=46.170 ms
64 bytes from 39.156.66.10: seq=1 ttl=49 time=53.166 ms
64 bytes from 39.156.66.10: seq=2 ttl=49 time=54.292 ms

Auto connect on startup

cat >> /mnt/system/duo-init.sh <<END
# Auto connect to WIFI on startup
wpa_supplicant -B -i wlan0 -c /etc/wpa_supplicant.conf
END
reboot

Using a premade wpa_supplicant.conf

See files/wpa_supplicant.conf. Copy it over to the device

cp files/wpa_supplicant.conf ROOTFS/etc/wpa_supplicant.conf

(WiFi/LAN) MAC changes everytime

echo "pre-up ifconfig eth0 hw ether 78:01:B3:FC:E8:55" >> /etc/network/interfaces
echo "pre-up ifconfig wlan0 hw ether 78:01:B3:FC:E8:55" >> /etc/network/interfaces

Colors are inverted

The display in this code uses 2 bytes per pixel. (BRG565) Yours might use different color coding. Use fb-set to get the bits-per pixel, fetch your displays datasheet and change the code in frame_buffer_display.rs accordingly.

I dont see anything

Check your display connections and you might want to install BR2_PACKAGE_FB_TEST_APP into your buildroot to test the framebuffer device.

not found

[root@milkv-duo]~# ./hello_riscv 
-sh: ./hello_riscv: not found

Create an symlink to correct the interpreter path used in the binary

ln -sf /lib/ld-musl-riscv64v0p7_xthead.so.1 /lib/ld-musl-riscv64.so.1

sftp-server not found

scp target/riscv64gc-unknown-linux-musl/release/hello_riscv [email protected]:~
[email protected]'s password: 
sh: /usr/libexec/sftp-server: not found
scp: Connection closed

Your ssh client is newer than on the host. Use the legacy options:

scp -O target/riscv64gc-unknown-linux-musl/release/hello_riscv [email protected]:~

Why does my MilkV get a new MAC address and IP everytime

Yet unsure, i guess they didnt pay MACs. Which could be why the MAC addr. are super random everytime.