Amazing! Waiting for just this tut

@Coding Neko asked a useful question. "Why learn RISC-V assembly [language]?" The video could say: 1. Learning assembly on any CPU helps understand what's _actually_ happening, and may help debugging. 2. Learning assembly for a RISC-V is rarely useful (except for point 3). C compilers for RISC ISAs mostly generate better code than an assembly programmer could write in comparable time. So C is much more productive. 3. Learning assembly for RISC-V might be valuable for writing: a bootloader, 'bare-metal' startup code (eg. code to replace program initialisation like 'C pre-pre-main') porting or implementing multi-tasking, or bootstrapping a programming language that isn't in C. There might be a few other cases eg: super-fast interrupt handlers, or porting performance-critical assembly from a different architecture. Some cases might be easier to write a C program with in-line assembly, but that still needs assembly knowledge. Problems where assembly might be essential involve resources C programs can't access (eg a CPU status register), or instructions the C compiler can't generate. However there are often 'C intrinsics' which generate those instructions, so needing assembly is rarer than it might seem. 4. Learning RISC-V ISA programming is better than learning a proprietary ISA because RISC-V _is_ open. Unlike other open ISAs, affordable hardware exists from multiple manufacturers, and RISC-V is increasingly being embedded in products. Summary: Understanding the underlying hardware helps us debug higher level languages eg C programs. The cases where assembly is _essential_ will likely become obvious quickly. 'C Intrinsics' might remove many needs for assembly language programming. Writing in-line assembly within a C program is often much easier than only raw assembly. Code space is rarely a problem compared to RAM, so don't worry unnecessarily about program size. With those facts, people have enough to reach rational. informed. decisions _(It took me under two minutes to read that out loud at my normal pace; so, not much extra.)_ It might be worth spending a minute or two on why the C compiler will likely do a better job generating code for a RISC architecture than most assembly programmers could do. I am not trying to dissuade anyone from learning RISC-V assembly language. I'm only trying clarify the reasons. Best Wishes All for 2022. (Sorry for repost, I spotted some mistakes.)

Now that is a real good tutorial ! No long bullshit talks just to increase viewtime... straigth to the point, enough to get going, the rest is just a mather of figure it out yourselve (if unable, you're unable to code any assembly anyhow)

Concise! Keep it up! Very High Quality!

I learned Assembly on this board about 2 years ago. I want to mention few things I noticed that were wrong/need more info to save others from days of banging their heads against the wall. When I first tried to do this, I rather quickly accidentally overwrote their bootloader program by putting all my code at 0x2000_0000. So maybe that changes made some of these things more important and would have handled for me otherwise: --The FE310 is -march=rv32imac not -march=rv32g. The g is shorthand for imafd. The fe310-g002 does not have an FPU (fd). It doesn't change anything in your code because you aren't using any floating point instructions but I thought I would mention it. --You did not setup the Clocks. However, with real serial hardware, you need to set the baudrate by setting up the core clock frequencies multipliers and dividers, and then setting up the dividers on the UART. --GPIO IOF is missing from the GPIO memory offset table in the FE-310 manual. This is probably the biggest issue. To actually be able to connect to the GPIO and interface with the UART, you need to set the GPIO operation mode to the alternate function corresponding to the UART on those pins. But the docs don't tell you where that configuration register is. I'll post a reply with that info later today. I don't have my notes on where it is in front of me right now. --Maybe GNU AS doesn't care, but that should be "addi a0, a0, 1" not "add a0, a0, 1". --Keep in mind that la, li, btlz, beqz, csrr, jal, ret, and maybe depending on my previous point add, are all pseudoinstructions. The reason I bring it up is that jal in full-form takes a register to use to form the link. This defaults to ra. ret is actually encoded as jalr zero, 0x0(ra). It is a jump to the value in the register with the link set to the zero register. It is kind of like piping to /dev/null. It is just gets sent to a black hole. So you'll need to either use different registers to link or start saving them on the stack if you want to start nesting function calls (jal/jalr). I personally really hated the choice of a USB type-C port. I had to go out and buy a cable specifically for this board, rather than be able to use any of the Standard, mini, or micro USB B cables that I had lying around. This board also uses a Spark-fun proprietary connection QUIIK or something like that. I've never used it, but this board is actually based on a SiFive design. I think it was the SiFive Hi-Five Freedom Freedom Everywhere. My understanding is that it is very similar without the proprietary connections and a multi-color LED, instead of the fixed red one on the Sparkfun Red-V.

I feel lucky to find this channel.

Thanks for the content

A deeper dive into linker scripts will be awesome as well. As always great video! Archived.

Great content and didatics!

I really really really appreciate that you did this video for the asm newbz to riscv, but if I'm being honest, I left feeling even more intimidated by the amount of code I was unfamiliar with...

Thank you very much!

Excellent introduction. A deeper dive into this board/programming would be appreciated. Also as Trumpet Sock mentioned, a deeper dive into linker scripts would also be appreciated.

Wait wait... wait. Multithreaded programs in assembler? Is anyone that masochist to even try that?

Low level gang!

It has been a very long time since I have done anything in assembly language. Many years ago I had a Heathkit 89 Computer which had a Z80 processor. I did do some simple things in Intel 8080 assembly language.

Hey very nice tutorial 👍 Could you maybe make a tutorial how to use the gpio on the sparkfun red-v

Holy cow, i was already subscribed?!? haha

Hope you do a video how to setup rust to code for a RISC-V

It would be nice to see that difference between the compiled binary and the hex file.

I might be missing something but wouldn't it be better to explicitly jump to halt after returning from puts. Works fine here but it's cycling through puts_leave with a0 pointing to the null, but in a more complicated program you might run some code without intending to.

However the capacity of the on-board flash chip is 32 Megabits(Mb) instead of Megabytes(MB) according to the official schematic.

Interesting, only ~46 instructions in the ISA, I don't know, looks limited for efficient use of all resources; but being Open Source and getting powerful, it looks a worthy ARM competitor; My God Is Full Of Win

Where can I find the manual for riscv that explains how I need to setup my linker script?

At 11:25, I do not understand how you got to the address 0x20010000? Where is this mentioned? I searched for the manual pdf of the RED-V SiFive chip and it said in chapter 5 "Boot Process" a table, but it says a very different number? Edit: I was looking at G003 manual. In the G002 manual for the E310 it did say 0x20010000.

I think learning SOME assembly language will teach you a lot about what's actually happening under the hood. And if you are trying to create very fast code, you can ask Compiler Explorer to show you the assembly code for your Rust or C code and see whether it is what you expect. OK, but that would be true for ANY assembly language, so why RISC-V? First, because RISC-V is about the easiest, most straightforward ISA you will find. You won't gain any extra insight into what the hardware does by learning a mess like the x86 ISA, and that would be a LOT more effort. And RISC-V is probably going to be a BIG DEAL in small embedded systems, so knowing it could help you in your career a few years out.

Could you perhaps look into trying out running riscv code on a Longan Nano a gd32v board. Is quite inexpensive and great for beginners!

Nice! Why not define a .uart section in the linker script to make everything relocatable?

nice vid

Great video. Unfortunately the Sparkfun RED-V seems to be out of stock. RISC-V boards can be hard to get.

You could revisit that topic utilizing Makefile with targets board and qemu, dynamically creating apropriate linker scripts. Totally not a demand, just idea to keep series alive/ start series. also - for sake of education value, it would be valuable to mention that address $20001000 didn't came out of thin air but is based on si5 documentation -> e310 manual -> table 9 [memory map] same for qemu's entrypoint. i mean - yeah, this video isn't targetted at average Joe bored with funny cats videos so searching for some other entertainment, but me personally i always had hard time digging trought datasheets and cherrypicking valuable info. Knowing where too look at and what to search for creates pathway in brain for the future :)

What starter kit would you recommend these days? Sparkfun hasn't had them in a bit and they don't seem to have an estimate for when they will be back.

I like the $8 ESP32-C3FH4 RGB board.. it has a Risc-V but also includes Wifi, Bluetooth5, couple buttons, 25 leds, etc. However, not sure how debugging works on it. For example, I understand gdbserver runs on the target cpu, and that the host cpu must interact with it using openocd/jtag... but what's the general approach on setting that up? I know Percepio sells a "Tracealyzer" that can save snapshots of your FreeRTOS project, for analysis. Perhaps the same is true with CodeWalker and Micrium uC/Probe? I'd like to see real-time live streaming of the data. BTW, any thoughts on the 'Timeless Debugging' talk given by the legendary George Hotz?

This is much easier than the complex fooling around I have to do on an STM-32.... it's like a return to the simplicity of the AVR.... maybe even simpler.... I certainly have to look into this chip.... it's not just the RISC-V, it's how easy they've chosen to structure the microcontroller's peripherals too. NOW if someone would just bring out a board without all that SPI flash, USB port and other things I don't need for Blue Pill prices.... now that would be delicious.

Looking at a thumbnail I thought the red board was MSP430

Wow! So does the document saying how to link a program to the board come with the board?

please make a detailed video on qemu emulation please please

The finished code is shown at 10:06. Don't you need something after calling the function *("jal puts")?* I would think jumping to halt *("j halt")* would be appropriate. As it is, it looks like you'll fall through and execute *puts()* again with no return address on the stack.

I keep wanting to buy one of these and a book on RISC-V assembly, but it feels like I should wait for something a little more powerful.

how much should i know to do this i m taking a computer science degree and i m in last year i know only basic commands like ld,sw,jal, etc

So QEMU automatically prints the data that is written to UART to stdout?

does it have any type of cas or faa instructions for multi threaded data structures ?

Hey this is random video to text on but can anybody guide me on how to start understanding low level stuff. Let's say i want to reach a level where I can program an micro controller in assembly by looking at its documentation 😅

Still trying to get my raspberry pico to work with something more complicated than blink so I'll skip getting one for now

Could have jumped to halt at the end.

A little bit of forethought before leaping into programming can save a lot of keystrokes and debugging time. A lot of that code looks like boilerplate that will be used repeatedy, in every program for the board. It should be set up beforehand, then included as a starting step, by whatever mechanism the local editor supports. The same is true of the compilation and linking steps. A lot of unchaninging operations, with only the program name changing. All that should be in a script.

thank u i love u

Can yiu code doom to see if it moves faster then on my 150mhx SGI indy

On the physical board I am somehow stuck. In your example you have msg in .rodata (that is read-only) and that works If I move msg in .data (that is read/writable) then a letter "C" is written and not the string, so somehow the message string is not there or I have a wrong pointer. I think I need a boot.s that is more extensive than setting up a stack and getting the Hardware thread 0. I assume that .rodata is running in flash memory and .data needs to get copied, but I can't find the way to do it so far by surfing on the internet. A more advanced boot.s example would be nice in this demonstration.

Why did you provide the _end symbolwhen you never used it?

150 MHz early laptop? I wish... The first laptop I used was 10MHz or so.

taque is the french word for hyphen.

Nice vid, but I'm not so deep in low level asm stuff, I'm a Rust programmer. What would you recommend to watch/read to understand what is going 'ere? (I'm interested in RISC-V as an open architecture)

Suspect there are flags for clang to build too riscv?

can you make an update please sir ? there is a shortage of this type of content ! and there is a big updaTe to the hardware available

Not Five, V for Versatile!

This is all well and good, but how do you write a preemptive multitasking operation system for it in assembler? Subbed

Use larger characters. 24 by 80 is ideal.

you didnt mention how much ram that puppy has?

New ESP32 devices are based on risc-v.

How many boards have you zapped with poor handling from ESD (static discourage)?

that is not nearly as convoluted as I would have imagined.

Why learn RISK-V? Or any other assembler language? 1. Because assembler is way more easy than any programming language. No OOP, No traits, no abstract syntax, no 1000 dependency packages, different frameworks.... Just you and your processor. 2. Force your brain to get out fo your comfort zone and become more creative. Even though you may never create big projects in assembler unless you are a virus writer. The knowledge can even help you create better high level code. 3. You are more focuses on your code you write. Every deploy is slow to debug so you must look at your code mere thoroughly and understand the code way better. Sloppy code will punish you big time, so quality code is enforced. 4. Learn to create efficient code, not bloated code like you used to have in any higher level programs. Your high level projects will improve.

"Same price" 42$ is not the same price xD

The blur on video is so horrible.

Which linux distro are you using?

Hmm VMware or virtualbox but it looks more like VMware

what language is this? *.s file?

The best board to learn RISCV is QEMU.

Step 1: Implement a RISC-V CPU in FPGA Step 2: learn RISC-V asm Am I doing this right? 😂

You call (jal) your puts routine and then NOTHING! You just let it fall into the puts routine again!! Surely you want to halt or loop or something after calling puts?

I don't...What's the point of this? Why would you code RISC-V Assembly instead of C? is there any actual advantage or is it literally just to flex?

Stop saying "boom".