Hello, all!A quick question: if I want to transfer data between 2 STM32 devices, which are located 1 meter apart, at a rate of at least 20Mb/s, in bursts of 300KB at a time. what is the best way to do so?The communication is unidirectional.I suppose my options are either :SPI (which I'm not sure about, because I understand it's only good for up to ~30 cm)8 parallel data lines with a clock, which allow me to effectively cut the bit rate by 8, but I don't know if it will actually be reliable and if suitable cables with enough wires are available for purchase.Some other possibility I'm not thinking about?Thanks!

Associate III

Question

Best way to transfer fast data over 1 meter cable

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Hello, all!

A quick question: if I want to transfer data between 2 STM32 devices, which are located 1 meter apart, at a rate of at least 20Mb/s, in bursts of 300KB at a time. what is the best way to do so?

The communication is unidirectional.

I suppose my options are either :

SPI (which I'm not sure about, because I understand it's only good for up to ~30 cm)
8 parallel data lines with a clock, which allow me to effectively cut the bit rate by 8, but I don't know if it will actually be reliable and if suitable cables with enough wires are available for purchase.
Some other possibility I'm not thinking about?

Thanks!

This topic has been closed for replies.

AvaTar

Senior III

> I suppose my options are either :

SPI (which I'm not sure about, because I understand it's only good for up to ~30 cm)

With proper drivers (I mean hardware) and homogenous, impedance-matching cables, this works.

I had been on a project that successfully used SPI over ethernet patch cable as means of communications.

A higher level protocol to detect and correct transmission corruptions is advised, though.

ISeedAuthor

Associate III

Thanks! These drivers, are they independent HW components I can look for, at, let's say, DigiKey? How are they called?

Do some STMs happen to have those on board?

AvaTar

Senior III

> These drivers, are they independent HW components I can look for, at, let's say, DigiKey?

Yes, so much I remember. But not a specific name, it was more then 6 years ago.

In general bus drivers with an output impedance matching that of your cable. Ethernet cable and RJ45 connectors are a relatively cheap solution.

Perhaps differential drivers for RS485, CAN, or similar. The transceiver chips are usual not specific for said protocols, only the bus levels. Bandwidth should be sufficient, I would say about 100MHz for a digital 20MHz signal.

Or asymmetric one's, like 74 series bus transceivers.

After Forever

Senior III

This might help - Extending the SPI bus for long-distance communication

ISeedAuthor

Associate III

Thanks! reading now

Tesla DeLorean

Guru

Ethernet

One could likely fake a version without magnetics for point to point.

Tips, Buy me a coffee, or three.. PayPal Venmo (See Profile) Up vote any posts that you find helpful, it shows what's working..

S.Ma

Principal

Ethernet is good.

Backup would be monodir link

Check on DS90LV031A cmos to lvds to cmos

Uwe Bonnes

Chief

20MB/s and 100 Mb Ethernet does not fit together. 20 MB/s is > 160 Mb/s.

Does the llink need to be bi-directional? Does the link need to be flexible with a cable or can it be a backplane. Maybe some serdes chip connected to the FMC can do the job.

Otherwise STM32MP1 has Gigabit Ethernet.

AvaTar

Senior III

I think this is an ambiguity in the OP.

SPI would not be able to manage 20MByte/s, neither would the receiver really be able to sustain this data rate for sensible package sizes.

I suppose he meant 20MBit/s.

Dvorak.Peter

Associate II

My 2 questions are:

Is power and ground common to both devices.

Is this link ever unplugged

ISeedAuthor

Associate III

Yes, the ground is common.

They work only with each other, connected via a connector that I'll add, depending on the chosen protocol.

Dvorak.Peter

Associate II

I would use :

SPI

Ethernet 1m CAT5 patch cable

RJ45 connectors

RS422 tx rx chips or RS485 transceivers

100 ohm termination on each pair

Make sure that on the receiving side you sample in the middle of the data cycle.

TI SN65HVD7x 3.3-V Supply RS-485 With IEC ESD protection is rated up to 50Mb/s

http://www.ti.com/lit/an/slla173a/slla173a.pdf

S.Ma

Principal

Both the transeiver which diff the signal and the peripheral in the MCU must sustain the speed.

Otherwise, multiply the peripherals on each side to widen the bus...

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