Meridian Unplugged - Powered by MrTechGuy.co.uk Forums Discussion Off Topic USB to RS232 (Raspberry Pi)

I'm writing a remote control app for the 500s via Raspberry Pi so can any one suggest a good cable.

Hi,

Try a Google Searching (see link above) the forum for "USB RS232", there are plenty of discussions and recommendations.

Regards,
Carl

EDIT: Sorry, just read Ian's post ... I was thinking for PC/Mac use not Pi.

I've used both Prolific and FTDI chipsets on Pi with equal success. You will however need to search some Pi forums to check exact chipset designations as not all Pi drivers are available for all versions of chipsets. iirc that it is the older chipsets that are affected so if buying new it may be supported by default in a particular Pi OS. As most USB/Serial devices don't list the exact chipset designation in their spec, it's probably a case suck it and see and returning if it does not work.

You may find a spurious issue (total lockup) though with running both USB/Serial interface and a Wifi dongle. The only reliable solution that I found was running with a powered USB hub or, as I do in non dev environment, with the wired connection. Later Pi versions may be better (a new PI was launched today April 1st) than my Model B rev 2, but it was an intermittent problem that occurred within a few minutes to few days of use.

I recently rebooted my Pi/USB-Serial connection down after nearly 9 months 24/7 use logging data on 4 second intervals. So it's a pretty reliable solution.

Do you think it's a power issue then?
I've built an external 5v 2A PSU for my Pi will this help?

It's very simple, a 15v output toridal in to a rectififer bridge, smoothed by 2 10000uf 63v caps then a regulator to give me 5v 2A.

I don't think it's anything to do with the PSU, within reason. As I understand it, it's to do with the maximum power that Pi can simultaneously supply to its peripherals. Exceed that, Pi hangs with no diagnostics.

But shouldn't that be down to the PSU? I'm certain that if you provide the amps the Pi can supply the power.

If not... would I be better using the second output from the toroidal to create a second 5v 2a into a USB hub, then run the serial from that?

All I can say that from experience, Raspberry Pi can suffer random voltage droop due to USB issues that will result in a total lockup even when the power supply exceeds the maximum current draw for Pi and all directly connected devices.

This does not happen when using same power supply into a powered USB hub with USB devices connected direct to the hub. My power supply is specifically designed for Pi and exceeds all required specification.

As I say, later models may be better. I have a couple of rev 2 model B's. Rev 1 Pi's had an internal fuse that would blow with USB overload, removed on later models and revisions. The underlying issue has not gone away, it's just that Raspberry Pi's are not specifically protecting for it.

this may shed more light on subject

Fwiw, my wifi dongle is a low powered edimax nano dongle.

Thanks for the advice. I use the Nano dongle as well.
I'm still gonna give the remote program a try, I'm off work for 5 days so it's either program or go shopping with her indoors and I know which I'd prefer.

Ian - if you're referring to The Pi Hut's announcement of the Raspberry Pi Model C - it was an April Fool. Sorry!

D

Hence the date in my post!