# RISC-V chip with USB to serial



## bcomputerguy (Nov 21, 2017)

I wanted to do a little test application based on the SiFive RISC-V microcontroller so I ordered some of those chips.

I didn't order the PCB because I don't think that's necessary from my project, I just want to put it on a breadboard to get power and do some small tests, plus that's extra hardware that I won't need in the final app.

Without the little Raspberry PI like PCB with the USB to Serial adapter, I'll have to wire up a USB to serial to connect to the board while developing and then remove it once the application is complete.

Here's the product data sheet: https://www.sifive.com/documentation/chips/freedom-e310-g000-manual/

Are there any preferably USB type devices that would be recommended? Something with good compatibility with FreeBSD?

If I am posting this in the wrong section please help me put it in the correct place.


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## Phishfry (Nov 21, 2017)

Prolific PL2032 is what I use. FTDI is well supported too.
There are 1.8V, 3.3V and 5V TTL versions but you don't really use the power anyway. Just rx,tx and ground on the Pi/BBB/ARM

I looked at the manual. It is not useful at all. The datasheet has more details, like that it needs 1.8V and 3.3V power.
The block diagram 1.1 in the manual shows UART but does not list voltages.

I am assuming since this is a SOC package then the UART should be powered through the silicone.
Some boards the UART was a separate package and you had to put power to it.

Are you trying to run FreeBSD on this? Is it know to work at all? Does it use u-boot?


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## bcomputerguy (Nov 21, 2017)

Phishfry said:


> Prolific PL2032 is what I use. FTDI is well supported too.
> There are 1.8V, 3.3V and 5V TTL versions but you don't really use the power anyway. Just rx,tx and ground on the Pi/BBB/ARM
> 
> I looked at the manual. It is not useful at all. The datasheet has more details, like that it needs 1.8V and 3.3V power.
> ...



I won't be running FreeBSD on this one, I'll be using this as a microcontroller but I'll be doing the development from FreeBSD.

FreeBSD does boot on the RISC V rocket core





My main purpose is to test out the board and see what it's capabilities. RISC V is new and totally different direction being open source and royalty free.

I'm sure I'll encounter bugs but I'd like to support the project and spread the word.

The issues you noted while looking at the manual and data sheets are just a few of those "bugs". I'm sure they have the info but this is their first product.


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## Phishfry (Nov 21, 2017)

I do see that risc-v has a kernconf here on -CURRENT
`/usr/src/sys/riscv/conf`

From reading some docs it uses berkley boot loader or bbl

https://people.freebsd.org/~br/freebsd-riscv.pdf


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## ronaldlees (Nov 21, 2017)

Phishfry said:


> Are you trying to run FreeBSD on this? Is it know to work at all? Does it use u-boot?



Outside of simulation (Spike) or emulation (Qemu), I think that currently the way you get FreeBSD running with RISC-V is with FPGA - meaning something like this:

http://www.lowrisc.org/docs/tagged-memory-v0.1/fpga/

For this purpose, maybe you could use the Freedom U500 dev-kit from SiFive (like the Zed, it's an FPGA board) - but IMO the U500 doesn't have pricing for anything but a very serious hobbyist or a professional.  AFAIK, the SiFive chip referenced by the OP is "Arduino compatible/style" MCU stuff.  If anyone knows of alternative FPGA boards that'll do FreeBSD + RISC-V, I'd love to hear from them, especially if they're low $$$.  But the Zed is known tested?/works? (as described in the link below), and is in the $ range of the hobbyist:

https://wiki.freebsd.org/riscv

The smaller "Arty" FPGA board can be used to do development for the little RISC-V MCU board IIRC.  I think they recommend the Olimex jtag be used in conjunction.


_Note: RISC-V is trademarked by the RISC-V Foundation_


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## bcomputerguy (Nov 21, 2017)

ronaldlees said:


> Outside of simulation (Spike) or emulation (Qemu), I think that currently the way you get FreeBSD running with RISC-V is with FPGA - meaning something like this:
> 
> http://www.lowrisc.org/docs/tagged-memory-v0.1/fpga/
> 
> ...


The RISC-V guys say they'll be coming out with a Raspberry PI like board in early 2018 that will be able to boot FreeBSD.

That will be something to keep an eye on as it progresses.


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## ronaldlees (Nov 22, 2017)

bcomputerguy said:


> The RISC-V guys say they'll be coming out with a Raspberry PI like board in early 2018 that will be able to boot FreeBSD.
> 
> That will be something to keep an eye on as it progresses.



Especially if it's priced like the Pi!!

But, I'd expect to pay a little more.  Thanks for the tip.


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## ronaldlees (Feb 5, 2018)

https://www.sifive.com/products/hifive-unleashed/

Quite a bit more than the Pi, but 8GB !


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