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12dstring

USB EQDir for under £4

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I don't wish to start adding transistors or owt else to it once it arrives cos I don't know what I'm doing- it needs to be a "dummies" version for some of us :icon_scratch:

I think Dave's pictures are as simple and as clear as it gets, it's only three components, and if you place the transistor as shown, with the legs connected as per the image then it shouldn't be a problem...

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Alternatively buy the 5V TTL version of the converter and then there's no need to shift levels... ;-)

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I've not had any problems with mine, however unmodified it will be more susceptible to noise so if you have a noisy power supply or nearby cables for example you'd be less immune to that noise and communication errors would be more likely.

If you've got a soldering iron then I'd recommend the mod even if it works without, as it's pretty simple and allows you to extend the cable if needed (10m as Glider says). It just pushes it over the £4 mark.. but only by a few pennies :icon_scratch:

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sorry to be a pain but , I know I can get the transistor from Maplins but exactly which resistor ought I be asking for ??

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To follow the pictures you'll need:

1 x 2N3904 transistor (although really any of Maplin's "Low Power LF NPN Transistors TO92 Case" will do)

2 x 10k resistors - 1/4W size (or Metal Film 0.6W from Maplin's are the same size)

The mosfet circuit doesn't have any advantages over the transistor one other than only needing 1 resistor, but I suspect people would be more likely to have NPN transistors lying around.

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Thank you very much Dave, that last line makes no sense to me tho :icon_scratch: but at least I know what to get and how to put them together !

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Beamish, trust me I have every confidence you can do this... If you get stuck I'm sure I have stacks of those transistors laying around in my hobby box and could post a few plus the resistors off to you - just drop me a PM if Maplin let you down...

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umm, bottom line is will Dave's original work ok for 3m or less of cable ? I don't wish to start adding transistors or owt else to it once it arrives cos I don't know what I'm doing- it needs to be a "dummies" version for some of us :icon_scratch:

There really is no simple answer to that question - it might work, it might not - it all depends on the quality of cable used, its length and the amount of inteferance around etc. If you're not happy doing minor circuit modes then the safe "dummies" solution is using a 5V ftdi cable as shown on the EQMOD web site - they only cost around £11 delivered (from tronisoft Tronisoft - Bluetooth RS232 Port / USB Serial Adapter Trade Distributors, Bluetooth to Serial, RS232 TTL Serial and RS232 IO board manufacturer).

Chris.

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I agree with Chris. The FTDI cables work really well with the SW mounts. They are a little bit more expensive, but are well supported with drivers and documentation readily available from the web.

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no harm in giving it a whirl :icon_scratch:

mind the tronisoft 5v ftdi is cheaper then when I first bought one for the HEQ5 (plus del =£20+ )

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you can get a barebones ftdi on an 28-ssop to 28pin dip adapter for about £7 on ebay, just got to add a couple of caps and resistor, failing that, the cheapest I have seen is about £3 but that's for an individual ftdi 232rl chip, you would of course have to make your own pcb to attach it to.

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I agree with Chris. The FTDI cables work really well with the SW mounts. They are a little bit more expensive, but are well supported with drivers and documentation readily available from the web.

.....and the driver remember which device was assigned to which com port. So you can plug the device into any available USB port without worrying that the COM port number will change (from an EQMOD support perspective I just love em! :icon_scratch:).

Chris.

Edited by chrisshillito

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ebay has loads of ftdi items, cheapest 5v device:

FTDI Basic Breakout for LilyPad Fio/Pro | eBay

Bear in mind that it doesn't have the RTS pin broken out so this board is useful for EQMod but not useful for things like a webcam mod, for webcam mods i would suggest something like this:

FT232RL RS232 FTDI USB to UART Breadkout for breadboard | eBay

As it can be breadboarded or soldered directly into stripboard (maplins do stripboard desgined to drop dip packages into with a gap between each side of the chip). Either of those boards are useful if you want to drop a usb to serial device into your project. The first link also has a handy dandy 'bridge' on the back which is set so that the gpio are 5v, easy to cut the bridge and solder bridge to the 3.3v IO signalling on the pad next to the VCCIO pad.

I must say, without doubt tht FTDI chips rock, they are incredibly versatile, you can use them as programmers for AVR chips (arduino microcontrollers amongst the many other chips atmel do), you can read/write epprom chips (like the one in the spc900/880nc webcams) and communicate with spi/i2c devices, there's even a £20 board that can do jtag!!

Edited by Reggie

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.....and the driver remember which device was assigned to which com port. So you can plug the device into any available USB port without worrying that the COM port number will change (from an EQMOD support perspective I just love em! :icon_scratch:).

Chris.

True. The PL2303 needs an external EEPROM to give the unit a "serial number". With that the driver also remembers ...

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which eeprom do they use chris? eeproms are pretty cheap and come in dip packages.

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Now THAT is something I was not able to find out. It's I2C but I guess they all are. The PL2303 datasheet didn't say what EEPROMs are supported. I was going to try that one day. The USB-to-Serial adapters I use have an empty place for an EEPROM on the PCB and I have a few 2k (IIRC) EEPROMs lying around. Didn't get around to it yet.

There is Windows software that allows you to program the EEPROM in-circuit through the PL2303 once it's soldered in place.

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Looking at a pl2303 datasheet it's a 2wire serial eeprom that's needed, 24c02, according to their reference design on this page: Welcome to Prolific

(top link)

which you can apparently get from fairchild:

http://willem.engen.nl/projects/DC5xx/FM24C03U.pdf

or atmel:

http://www.atmel.com/dyn/resources/prod_documents/doc0180.pdf

or ST-micro :icon_scratch:

Available on all the majors (farnell etc.) and ebay and of course places like www.sparkfun.com

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I think I'll give that a try soon. I have all components. It's just a matter of soldering the EEPROM on and test....

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Hmmm, I just finished soldering on that EEPROM. But it seems that EEPROM write tool doesn't work on Win7 x64. It says it can't find a PL2303 serial cable. Device Manager shows it as working fine. Looks like I have to find an XP machine to write the EEPROM.

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Yes, I've done that too - both ways round.

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