PICAXE URF and ERF Modules

Haku

Senior Member
BeanieBots, I just realised something, the code there is designed for the standard XRF/ERF modules buf if you've got the Picaxe specific ERF (with the inverted signal IO lines) you might have to change the "high XRFinput" to "low XRFinpuf", because I found the XRF input had to be pulled high or the XRF would think it was receiving data when it wasn't, and in turn that would cause it to randomly transmit 0's. Took me a while to figure that one out :)
 

Technical

Technical Support
Staff member
BeanieBots, I just realised something, the code there is designed for the standard XRF/ERF modules buf if you've got the Picaxe specific ERF (with the inverted signal IO lines) you might have to change the "high XRFinput" to "low XRFinpuf",...
Yes, and the serout baud polarity to N9600 not T9600

Couldn't get much sense out of either of those links. Maybe I'm missing something?
One is the source code, the other has a grey 'install' button which when you click gives you this link to the installer
http://www.ciseco.co.uk/downloads/XCM/setup.exe
 

BeanieBots

Moderator
Had the modules working "straight out of the box" with no issues.
Downloaded the XCM software and installed no problem.
Tried to use the "Download Config" button but got the following error.
"Reading ATBD

No valid response received
"
All the other bits downloaded OK. Is this because its N9600?
Not yet been brave enough to try reconfiguring anything. (like to make sure it works OK for a bit before messing! Took me ages to recover some issues with my XBEEs after messing with them!).
 

Technical

Technical Support
Staff member
As explained in the previous AT summary web links ATBD is not applied on the URF.
The URF doesn't normally care what the 'user' baud rate is - it simply sends/receives radio signals. It is the other end, the ERF, that receives the radio signals and then transmits the data out the microcontroller TX/RX pins at the correct baud/polarity. So it is the ERF baud rate setting that is important, not the URF.

With non-PICAXE ERF/XRF you need to use ATBD commands on the ERF/XRF to change the baud rate.
With PICAXE ERF the URF 'tells' the ERF what the computer baud rate is when the virtual COM port is opened, and the ERF then changes to that baud automatically, eliminating the need for ATBD commands on the PICAXE ERF.
 
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jedynakiewicz

Senior Member
Got the URF/ERF combo this morning. Plugged it together and programs download fine to an 18M2. Debug indicates good two-way traffic. BUT... the range is hugely disappointing. 500m in clear air, line of sight? Not yet tried this, but I moved the ERF (rigged up on an AXE091 platform with the 18M2) to another room in the house and no luck at all! Distance between the rooms? About 20m. Internal walls are brick, but I was just hoping that with an expected 500m clear air range I might be okay. So, I guess that I will have to start playing with some parabolic reflectors around the receiver... Does anyone have any other ideas about the antennae? Can I desolder the ceramic aerial chip and replace it with a quarter wave rod antenna?
@Technical; before I start playing with the antenna side, do the default AT settings start the devices on the full output power?
 

Technical

Technical Support
Staff member
Default AT setting is 10dBa.
Brick walls do kill off signals pretty quick, but before doing anything else re-positioning of the URF is probably the most important thing to try - try using a male-female USB extension lead to move it to a higher position a bit further away from the computer.
 

jedynakiewicz

Senior Member
Default AT setting is 10dBa.
Brick walls do kill off signals pretty quick, but before doing anything else re-positioning of the URF is probably the most important thing to try - try using a male-female USB extension lead to move it to a higher position a bit further away from the computer.
Wow! What a difference a 50cm USB extension cable makes! Thanks for that - and for the speed in the reply! I did have the URF on the right side of the computer in relation to the ERF and with the aerials lined up for correct polarity, but separating the URF out with the USB extension lead made all the difference in the world. The range is spectacularly increased and the ERF seems to transceive across the house without any problems now.

I think that perhaps a mention of the extension lead would be helpful in the RFA020/21 datasheet because it seems to make such an enormous difference.

I am looking forward to receiving the ERFs that I ordered so that I can really start to see what these things can do when used for chip to chip comms.
 

manuka

Senior Member
From my recall of the XRF- it's assumed these new URF/ERF will be similar: The 10mW (10 dBm) default TX power is pretty modest, & at -110dBm it's receiver is not that sensitive,especially when in proximity to the "RF soup" of a PC. Chip antenna, as widely used on the likes of 2.4GHz USB WiFi adapters, are generally only good for local work. In my 2.4GHz experiences they are NOT the sort of thing to tinker with either, although some scope for total bypassing may exist. Factor in that path losses increase with frequency (plus of course those brick walls) & your propagation path may indeed be marginal.

However, as mentioned several posts back, the salvation at sub GHz freqs. to such woes is that quite high gain directive beaming become feasible. Hence consider at least a reflective metal tray behind both units.

Naturally USB allows the unit to be raised above obstacles on extension cables, so first TRY THIS! At 2.4GHz such a simple extension can dramatically improve coverage- a significant factor in my 2004 era USB based "wokfi" explorations.

Stan.

UPDATE: Great-you've already tried USB to good effect! Active extension cables may be worth while too - these are capable of at least 5m extensions.
 
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srnet

Senior Member
Naturally USB allows the unit to be raised above obstacles on extension cables, so first TRY THIS! At 2.4GHz such a simple extension can dramatically improve coverage- a significant factor in my 2004 era
Indeed, you will be surprised how much Wifi or 3G coverage improves when the USB dongle is on top of a 7M pole. (5M standard USB extension + 5M active extension)
 

jedynakiewicz

Senior Member
Lots of helpful information in these posts, many thanks. Now can someone just confirm for me that I have the correct understanding of the behaviour of chip antennae? My understanding of the radiation pattern is that the chip antenna is omnidirectional and polarised. I have sketched a diagram of what I perceive to be the radiation pattern which suggests to me that the board is best mounted vertically for maximum omnidirectional range. If the chip is mounted horizontally then there will be two cones of reduced tranmission/reception range at the "poles". Am I correct in this?
ERF radiation pattern.jpg
 

MPep

Senior Member
@Jedynakiewicz,

I have previously put up a system using these 2.4GHz network patch antennae.
It was designed to provide internet access to ships in Lyttelton, which worked well.
These antennae were also installed, in a temporary fashion, on the vessels.

I came along, after the ships had been away for 6 months, and the crew had re-installed the antennae. Nothing wrong with this, but I noted that it was installed the wrong way around. No drop in signal levels were noted!!! ;)

I'd say that chip antennae are no different.
 

Paix

Senior Member
Indeed, you will be surprised how much Wifi or 3G coverage improves when the USB dongle is on top of a 7M pole. (5M standard USB extension + 5M active extension)
It has been my amateur radio experience with a handheld and an external antenna, that every four feet of elevation provides a significant improvement in TX/RX signal, up to the point that the limitations in the RX front end allowed the mixer to be totally swamped by adjacent channel signals.

So keep elevating your TX/RX, but if suddenly the performance drops, then the RX may just have become more visible to unwanted signals, not necessarily on the frequency of operation, but close.

For the most part if you are in a quiet part of the country, away from urban sprawl, then high and in the clear is GOOD. So much easier to put the TX/RX up the pole and run up power and signaling rather than incur any feeder losses or complications.
 

srnet

Senior Member
At some point in the next weeks or so I will be doing a comparison of the XRF versus ERF\URF over the local park, to check the effectiveness of the chip antenna versus the standard wire. It will be interesting to see how they compare.

Flat field testing, whilst it gives ranges that wont be achieved in typical 'urban' settings does allow a better comparison between different types of modules, that others can replicate.

A benefit of the XRF\ERF\URF is that you can turn the power down so that you done need a filed several kMs in size to carry out testing .....
 

Paix

Senior Member
The urban setting that I envisaged was the West Midlands where the level of amateur radio activity, for example, is relatively high, versus Peterborough or rural Lincolnshire where nary a signal is heard from one day's end to another. That any any other competing large signal sources in and around your frequency band of interest.

So I was thinking more of interference potential rather than attenuation factors.
 

MikeM100

Member
Recently received the above 'combo' RF modules but am having trouble getting them working ?

Installed USB com port driver for URF OK and heartbeat ticks away OK. Driving via (Hyperterminal 9600, 8 bits, 1 stop etc.) and Heartbeat LED flashes during transmission.

ERFwired as datasheet but not connected to PicAxe:

5v supply
CTS connected to 0V
Tx pulled down to 0V via 10k resistor)
RX floating
DTR to LED with 1K series resistor to 0V

Afterpower up the DTR LED flickers intermitently and on receiving a 'transmission' from URF sort of flashes but no data received on Rx pin ?

Any ideas ? I am surprised that DTR LED flickers - I was expecting a clean digital On/Off ?

signal
 

Technical

Technical Support
Staff member
Heartbeat on URF should be all the time, not just during transmission.
Do you have heartbeat LED on the ERF?

DTR LED flickers when activity on either TX or RX pin. It is a clean on/off signal - just brief!

You say RX is floating, but then how do you know if it is receiving data or not?

For trouble shooting try the serial terminal within PE, as HyperTerminal settings can sometimes be awkward to configure.
 

hippy

Technical Support
Staff member
With TX and RX linked on the ERF module, whatever is sent through the URF should be echoed back to it. This is perhaps the best way to tell things are working and a link from URF to ERF and back again is established.
 

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MikeM100

Member
ERF is wired as Hippy's thumbnail but Tx is pulled down to 0V via 10K. RX is 'floating' in that it is not pulled up or down. I am monitoring this pin with a 'scope' but see nothing at any time.

The DTR LED is constantly 'flickering' (looks like digital white noise) but momentarily goes solid during a transmission from URF.

More experiments this evening. I will link Tx & Rx as suggested - useful diagnostic !
 

hippy

Technical Support
Staff member
Tx is pulled down to 0V via 10K. RX is 'floating' in that it is not pulled up or down.
For an ERF, the RX is an input into the module, normally driven by a PICAXE SEROUT, the TX is the output from the ERF module normally going to a PICAXE SERIN.

It looks like you have those two swapped over, the floating RX perhaps causing random transmission that is causing the DTR to flicker.
 

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MikeM100

Member
Urgh - how silly of me - but the old problem of DTE and DCE confusion ! I even did the 'right thing' of pulling down the Tx input (except that it was the wrong pin).

I am sure this will raise a discussion here as to what the Data Terminal Equipment 'bit' is - PicAxe or ERF ?

Of course If I had hooked it up to a PICAxe all would have been fine - will try tonight and report back.
 

Technical

Technical Support
Staff member
Urgh - how silly of me - but the old problem of DTE and DCE confusion ! I even did the 'right thing' of pulling down the Tx input (except that it was the wrong pin).

I am sure this will raise a discussion here as to what the Data Terminal Equipment 'bit' is - PicAxe or ERF ?

Of course If I had hooked it up to a PICAxe all would have been fine - will try tonight and report back.
It can be confusing, which is why the datasheet is quite specific about PICAXE input/output connections:

Pinout (6 pin 0.1” (2.54mm) header, suitable socket part CON047):
01 – DTR – Connect to LED for RX/TX activity indicator
02 – RX - Data in, connect to PICAXE serial output
03 – TX - Data out, connect to PICAXE input
04 – PWR – 3 to 5V supply
05 - CTS – Chip enable, connect to 0V to enable module
06 – GND – 0V supply
 

MikeM100

Member
Humble Pie Time (Bit like Raspberry)

Swopped Tx & Rx pin function and they work perfectly ! Such was my excitement at receiving my new 'toys' that I must admit that I did not exactly read the datasheet, err completely. I printed it out and just looked at the wireless cable download circuit and sort of misread it ! The datasheet pin out description (on the same page no less) does describe the connections perfectly clearly. Being just slightly peevish I might argue about their naming but I would soon stand down.

Thanks Hippy & Technical - I will remind myself what RTFM means.
 

Grogster

Senior Member
Yummy!
I love humble pie!!!
Afterall, I have baked so many of them myself... ;)

Thanks for sharing, and being honest about the mistake.

If it makes you feel any better, I(and I have no doubt others here) have got confused as to from which end of the link TXD and RXD are reffering to - easy mistake to make, and can cause lots of brain-strain, as you have found out. :D

I have to say that I like the OpenLog way of labeling RXD and TXD pins on their OpenLog module.
TXO(data out) and RXI(data in) with respect to the module. I tend to copy that labeling for my own sanity later on.
 

BeanieBots

Moderator
Being just slightly peevish I might argue about their naming but I would soon stand down.
A common mistake indead!
As a general rule, you won't go far wrong if you always consider the labels on a device to refer to THAT device. That is why you will nearly always end up with Tx from the sender connected to Rx on the receiver and vice-versa.
If you think about it, any other convention would lead to even more confusion! (output from devide to input of the other device)
 

hippy

Technical Support
Staff member
Measured by sight and an uncalibrated rule so approx -

URF : 39mm x 25mm ( PCB ) / 55mm x 25mm ( including USB connector )

ERF : 35mm x 19mm ( PCB )

XRF : 28mm x 25mm ( PCB )

No scales to hand I'm afraid.
 

ThierryP

New Member
Measured by sight and an uncalibrated rule so approx -

URF : 39mm x 25mm ( PCB ) / 55mm x 25mm ( including USB connector )

ERF : 35mm x 19mm ( PCB )

XRF : 28mm x 25mm ( PCB )

No scales to hand I'm afraid.
URF ~ 5g incl USB connector
ERF ~2g incl 6 pins header
 

Pauldesign

Senior Member
Thanks Hippy and Thiery for the approx dimensions.

I hope Rev Edu includes an exact dimensions in the respective datasheets, because that's very vital :D .

I'm busy prototyping a novel key holder wireless device for our national technology innovation competition, so i thought of using one of those.
 

ciseco

Senior Member
The documentation states that there is an option to use a ERR/URF operate at 433MHz, but at reduced range. Does anyone know what the percentage reduction in range could be expected when opeariting at 433MHz?

As the reduction is probably due to detuning of the on-board chip antenna, would it be possible to remove this and replace it with a socket for an external antenna?
Hi,

The antenna and the balun (small orange object with 6 legs) are both tuned to 868-915Mhz, outside this range they will both filter the signal considerably (so reduce range). There's a 433 balan and that works well (forthcoming 433Mhz XRF), the chip antenna there's no direct size for size part for (the 433 part is much larger) so the chip antenna'd parts will always perform best at 868-915 and would need redesigning.

The range of the TI CC is extremly good with the chip antenna (far better than anything competitive) but for ultimate range, you'll need an XRF and external antenna (whip or SMA).

Hope this helps a little in explaning what is happening where.

Miles
 

ciseco

Senior Member
There was a question of polarization, the chip antenna (when flat) is vertical (imagine XRF with wire whip being vertical). Having chip antennas in similar orientation will give the best reception.

The URF ground plane is extended by your PC, so in some circumstances the PC has a positive effect but this is rarer than not, so extending the URF by a USB extension lead can improve reception.

The chip antenna and baluns are made by Johanson and are the CC1110 matching parts for anyone interested (uber geeky)



I'd like to mention a huge personal thanks to everyone who have bought them, the guys at RevEd for the vision (and patience with us) to give you guys remote programming and look forward to some weird and whacky projects :)

Miles
 

Grogster

Senior Member
I have a couple coming from TechSupplies to tinker with. Quite keen to see how they go, but I am not actually expecting that fantastic in terms of range, as here in New Zealand, the default frequency of 868.3MHz is, I think, illegal here. I will have to have a look on the Radio Spectrum Management website...

What this means, is that I will have to set them for 433MHz, but as already mentioned by others, this WILL effect range, as I would expect, as you are essentially de-tuning the antenna if not used on 868. :D

If I find the relevant information for NZ, I will post it here.

...or we could just wait for manuka to spot this and let us know! ;)

EDIT: Attached is the NZ RSM info, for any other Kiwi's here. 868.3 is NOT legal here, so if there are any other NZ'ers here with these modules, you need to move the frequency to 433 to be compliant with NZ regulations...

868MHz.jpg

869.025 - 870.015 is unallocated here in NZ - I don't suppose you can shift the frequency to here with commands? This is only 1MHz or so from the default frequency, and would still be a pretty good match for the aerial on the modules. ;)

864 - 870 is also GURL here in NZ, and also not far away from 868.3...
 
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jedynakiewicz

Senior Member
From the specification in the original ERF modules that the PICAXE versions are derived from, I understand that there is software support for 315/433/868/915Mhz (physical circuit is tuned for 868-915).

The following AT commands determine the frequency in the original ERF modules:
ATCH
Implemented in XRF/ERF firmware version 0.03 and above, URF firmware version 0.01 and above
Radio frequency – not actioned until applied (ATAC)
1 – 915MHz
2 – 903MHz
3 – 868MHz
4 – 433.5MHz
5 – 868.3MHz (default)
6 – 315MHz

ATCN
Implemented in XRF/ERF firmware version 0.28 and above, URF firmware version 0.01 and above
Radio channel number – not actioned until applied (ATAC)
Range 0-FF (255 decimal)

ATCS
Implemented in XRF/ERF firmware version 0.28 and above, URF firmware version 0.01 and above
Channel spacing in kHz – not actioned until applied (ATAC)
Range 1-FF (255 decimal)
Default C8 (200 decimal)

Perhaps there is something in the upper range that may be legal in NZ.
 

ciseco

Senior Member
Hi

Apart from the preset's it is possible to set anything supported by the TI device. If NZ is anything like AUS then you need to be on a centre frequency slightly above 900Mhz but then google gave me this to go on.

From time to time, small cordless devices which comply with overseas radio regulations are imported into New Zealand. For example, some may be designed to operate in the US ISM (Instrumentation, Scientific and Medical) band, which is 902 – 928 MHz. This does not align with either the NZ ISM band frequency allocations of 915 – 928 or the NZ cordless telephone band of 864 – 868 MHz.

I'd plump for 915 which is incidentally similar to the US

Stan will know the answer to this for sure.

Miles
 

manuka

Senior Member
Band regs. & allocations in the sub 1GHz frequency spectrum seem globally in a near continual state of turmoil. This arises from pressures (both at lower & higher freqs) and of course technical developments. A few reasons that spring to mind are-

1. Semiconductor gear for these (once considered high) frequencies is now reliable,sophisticated & cheap.
2. Cellular service demand (especially long range 4G at 700/800 MHz)
3. Closure of analog. UHF TV in favour of more efficient digital services.
4. 2.4GHz band considered increasingly cluttered & noisy
5. "900 MHz" offers better building penetration than 2.4GHz
6. "900 MHz" antenna can be higher gain & more compact than 433 MHz
7. Path loss at "900 MHz" is lower than 2.4 GHz

Here in NZ (New Zealand) the <1GHz MHz Radio Spectrum Management (RSM) regs. are a fruit salad of dicing and slicing, but the attached (officially gazetted 31st May 2012) may offer some help. From this resource it seems that 915MHz is locally only allowed a puny 3mW power, so 864-868 MHz (where up to a paint blistering 1W is allowed without freq. hopping) may better suit.

Note- Australian regs. (in both radio & electrical fields) are usually VERY akin to NZ's, but they annoyingly look to differ at this <1GHz slot. ACMA (Australian Communications and Media Authority) "900 MHz" regs. however date from the early-mid 1990s, & surely must have been revamped since then? Stan.
 

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Grogster

Senior Member
These modules are only for tinkering, at my end of things.

I have some SunrayRF modules anyway, factory set to 458.54MHz(and eight other frequencies in that band), where we can run up to half a watt, although, I am only running 100mW on that frequency(-9.9dBW), and sporadically only - probably one blip transmission every four or five hours, so I am not hogging the band at any rate! I listened to 458.54 for about a week on my scanner, and heard not a single blip, so it is a pretty clean band here in NZ in my location anyway, and with 100mW transmit power, it has a fantastic range.
 

MPep

Senior Member
I'm not so sure about using 868.3 for private use as this sits right in the TX band, look up on NZ RSM PIB23, page 261. Check here.
This is a licensed band, Crane control being a specific sub-set of the TX band. This band allows 16dBW (39W) and is wideband (25kHz).
 

manuka

Senior Member
As outlined in my post #75 above, NZ regs. allow just a very puny 2mW TX power at 868.3 MHz. The very nearby band 864-868MHz however allows up to a 1 Watt.
 

Technical

Technical Support
Staff member
Two new simple wizards to enable customers to easily change the ERF and URF frequency are now available at

www.picaxe.com/downloads/URF.zip

Naturally both ERF and URF need to be at the same frequency in order to communicate!

We are also carrying out final testing on a more complex wizard that enables configuration of all AT commands - coming soon!
 
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