Hacker News Reader

Comment by ajross | Hacker News Reader

It's a much more capable device. The existing RISC-V instances (I don't know much about SiFive's offering per se, I'm just reading off their datasheet) are more comparable to ARM Cortex-M parts -- running in the dozens to hundreds of MHz, with an MMU and a real OS kernel (Linux, obviously, though surely there are BSD ports in the works).

Hardware has, in addition to the GPIO, UART and ADC/DAC that you're used to from Atmel, a USB 2.0 device controller (it says "OTG", which implies a host controller too, but sometimes people get this mixed up), a SD/MMC/eMMC controller for storage (no idea about SDIO) and gigabit ethernet.

I'm a little disappointed in the lack of wireless connectivity on the SoC, though I suppose you can make up for that with off the shelf USB devices (or a UART bluetooth radio).

View on HN

The chip linked is the E310G, which neither has a MMU or real OS kernel (same as Cortex-M). It also doesn't have most of the peripherals you listed (maybe you got it confused with their other, larger chip). It really is a Arduino competitor (though much faster).

That sounds like these boards are getting to the point they can handle decent audio/signal throughput. But I don't see anything about usb or adc/dac on the site?

If you want an arduino compatible device that can do audio processing, go for a Teensy board (https://www.pjrc.com/teensy/ , http://www.pjrc.com/teensy/td_libs_Audio.html)

72/120MHz isn't really enough to do "decent" audio/signal processing with low distortion.

You can probably get it to work with a lot of effort and optimisation, but there'll be very little room to do anything with it afterwards.

Afaik AC97 chips run at around 24MHz, are dedicated to the job, and even they stop at 20 bit resolution and sticking the data onto a data bus. Getting better than that is "hard", which is why all the manufacturers pretty much standardised around such a low standard.

That speed is quite enough to do audio processing - you can run Opus easily on those microcontrollers. Many other audio processing tasks are simpler. AC97 chips are basically DACs/ADCs, and do no audio processing themselves, so are a bad comparison.

However, while most Cortex-M chips have an I2S peripheral to integrate with an external DAC, the HiFive1 doesn't, which might cause some difficulties. Audio out can be implemented with the PWM peripheral, though.

Depends what you mean by "enough".

24MHz is "enough" for 20 bits@96kHz ADC and some post processing.

But 20 bits@96kHz is not decent.

For reasonable SNR, you need at least 24 bits, and even then "the experts" offload to an external CPU http://www.tested.com/tech/pcs/454839-tested-why-high-end-pc...

For signal (less audio are more "controller") with high precision you need micro controllers with the power of at least an early 2000s PC (several hundred MHz and single cycle mul/div).

Raspberry Pi 3 is close, but it needs an external ADC/DAC.

Firstly, https://xiph.org/~xiphmont/demo/neil-young.html

Secondly, even if you did want to process at 96kHz, you'd have plenty of CPU left to do so. It's only 2x as intensive as 48kHz (this is a 32 bit CPU so using 16 bit vs 32 bit math is mostly the same, sans DSP instructions) and that amount of headroom is likely available, for example: https://www.rockbox.org/wiki/CodecPerformanceComparison

Thirdly, the article you linked talks about high end DACs but says nothing about the DSP on the card, other than that it has one, for doing... something (?)

Sigh,

Firstly, getting from uncompressed at the input to compressed is basic processing.

Seriously, you don't. Non risk instructions often take Multiple cycles, so you can only do a tiny number of them between samples, usually just enough to compress it to fit the bus speed without loss. https://en.m.wikipedia.org/wiki/Cycles_per_instruction

Thirdly, clearly you didn't rtfa.

Fourthly, go disagree on the teensy forum. https://forum.pjrc.com/threads/27364-Teensy-3-1-and-ADC-FIR-...

Most sensible people stick to 16 bits @ 48kHz, especially if it's not a pro-audio device but just something with a MEMS mic and 8ohm speaker.

And they would be interested in signal processing a 50kHz LF radio transmission why?

The Teensy audio adapter [1] uses a dedicated DAC, the SGTL5000. That frees up the MCU to do more DSP.

[1]: http://pjrc.com/store/teensy3_audio.html

I should have been more specific.

Radio signals below 50 kHz are capable of penetrating ocean depths to approximately 200 metres, the longer the wavelength, the deeper. The British, German, Indian, Russian, Swedish, United States [3] and possibly other navies communicate with submarines on these frequencies.

->That requires min 100khz sample rate.

You are correct. This first FE310 chip on the HiFive1 board does not have a built in ADC/DAC.

Reply on news.ycombinator.com