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105 lines
4.1 KiB
Markdown
105 lines
4.1 KiB
Markdown
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# Bare Metal Demo App
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This directory provides a minimal bare metal demo app that demonstrates how to easily create a bare metal C application and load it/run it on the CPU of a SoC.
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## Build and Load over LiteX-Term
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To build a LiteX SoC for the Arty board (available in LiteX-Boards) and build the demo app for it, execute the following commands:
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```bash
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python3 -m litex_boards.targets.digilent_arty --build --load
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litex_bare_metal_demo --build-path=build/digilent_arty
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```
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Where `--build-path` is the build path to the Arty build directory. The Arty board is used here but almost any another board supported in LiteX-Boards could be used. When no external RAM is provided directly by the board, `--integrated-main-ram-size` argument could be used to add some integrated RAM in the SoC and be able to execute the demo from it. (ex `--integrated-main-ram-size=0x8000` will add 32KB of integrated RAM).
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Loading the compiled demo app can be done in different ways as explain in LiteX's [wiki](https://github.com/enjoy-digital/litex/wiki/Load-Application-Code-To-CPU)
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Since our app is small and for simplicity we'll just load it over serial here: `$ litex_term /dev/ttyUSBX --kernel=demo.bin`
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You should see the minimal demo app running and should be able to interact with it:
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```shell
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--============== Boot ==================--
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Booting from serial...
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Press Q or ESC to abort boot completely.
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sL5DdSMmkekro
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[LITEX-TERM] Received firmware download request from the device.
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[LITEX-TERM] Uploading demo.bin to 0x40000000 (9264 bytes)...
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[LITEX-TERM] Upload complete (9.8KB/s).
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[LITEX-TERM] Booting the device.
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[LITEX-TERM] Done.
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Executing booted program at 0x40000000
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--============= Liftoff! ===============--
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LiteX minimal demo app built Dec 10 2020 17:13:02
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Available commands:
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help - Show this command
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reboot - Reboot CPU
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led - Led demo
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donut - Spinning Donut demo
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litex-demo-app> led
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Led demo...
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Counter mode...
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Shift mode...
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Dance mode...
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litex-demo-app> donut
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Donut demo...
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$$$$$@@@@@
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$##########$$$$$$$$
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###*!!!!!!!!!***##$$$$$$
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***!!====;;;;===!!**###$$$$#
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**!===;;;:::::;:===!!**####$##
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!*!!==;;:~-,,.,-~::;;=!!**#######!
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!!!!=;:~-,.......-~::==!!***#####*
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!!!!==;~~-.........,-:;==!!***###**!
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!**!!=;:~-... ..-:;=!!!********!
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;!*#####*!!;. ~:;==!!!******!!=
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:!*###$$$$#*! :;==!!!!!****!!!=;
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~=!*#$$$@@@$$##!!!!!!!!!!!!****!!!!=;
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;=!*#$$$@@@@$$#*******!*!!*!!!!!==;~
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-;!*###$$$$$$$###******!!!!!!!===;~
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-;!!*####$#####******!!!!!!==;;:-
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,:=!!!!**#**#***!!!!!!!====;:~,
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-:==!!!*!!*!!!!!!!===;;;:~-
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.~:;;========;=;;:::~-,
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.--~~::::~:~~--,.
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litex-demo-app>
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```
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## Replace the LiteX BIOS with the Demo App
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In some cases, we'll just want to replace the LiteX BIOS with our custom app. This demo can be used as a basis to create a such custom app.
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The demo will be recompiled to target the ROM of the SoC:
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```bash
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litex_bare_metal_demo --build-path=build/arty/ --mem=rom
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```
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The SoC can then be re-compiled to integrate the demo app in the ROM with:
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```bash
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python3 -m litex_boards.targets.digilent_arty --integrated-rom-init=demo.bin --build --load
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```
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When loading the bitstream, you should then directly see the demo app executed:
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```shell
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LiteX minimal demo app built Dec 10 2020 17:13:02
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Available commands:
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help - Show this command
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reboot - Reboot CPU
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led - Led demo
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donut - Spinning Donut demo
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litex-demo-app>
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```
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## Going further
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To create more complex apps, feel free to explore the source code of the BIOS or other open source projects build with LiteX on the [GitHub wiki](https://github.com/enjoy-digital/litex/wiki/Projects).
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