Single-Board Universal Module

More
19 Feb 2015 02:18 #28866 by mwm
Replied by mwm on topic Single-Board Universal Module
I believe you can find all the relevant sources at bitbucket.org/PhracturedBlue/universaltx . However, I've not been working on this (don't have a clue how), so I'm not positive about that.

If those are the sources, and any of you would like a shared repository to work in, let me know and we can create one and then add you to team deviationTx.

Do not ask me questions via PM. Ask in the forums, where I'll answer if I can.

My remotely piloted vehicle ("drone") is a yacht.

Please Log in or Create an account to join the conversation.

More
19 Feb 2015 02:22 #28868 by mikemacwillie
Replied by mikemacwillie on topic Single-Board Universal Module
I have 3 boards which I assembled quite some time ago. I had offered to send one to PB, but he seems to be taking a bit of a break. If someone else wants to take this on, I'd be happy to send one of my boards to them. It's cool that we're now up to a few people who can help build prototype hardware.

Please Log in or Create an account to join the conversation.

More
22 Feb 2015 06:17 #28992 by mikemacwillie
Replied by mikemacwillie on topic Single-Board Universal Module
PB committed his test code this morning so I could pick up on hardware testing. I've spent time on the module this evening, and can confirm that the signal loss is at the switch. I'm seeing about ~20dB of loss through the switch. With the switch bypassed, the PA is working fine with ~24-25dB of gain. These were measured with an RF probe, so they're not going to be terribly accurate.. but as relative measurements are good enough to show that the PA is functioning properly. I've verified that the switch control lines are being switched by the MCU correctly.

The PA TX_EN and RX_EN seem to be inverted for the NRF24L01, but that's not stopping testing. I think I remember this being an issue with the main repository anyways, and may already be fixed.


Up next is debugging the loss at the switch.

Please Log in or Create an account to join the conversation.

More
22 Feb 2015 17:12 #29003 by PhracturedBlue
Replied by PhracturedBlue on topic Single-Board Universal Module
I'm glad you found the same thing I did. I was thinking of doing a design using 3 2:1 switches instead. It would have slightly more loss, but I'd have better confidence, given that it'd be more similar to the reference designs I've seen. I wish I had a clue what was wrong though. I've checked the schematic and layout, and I believe I verified the select pins were actually toggling properly on the test board (it has been 6 months though, so I don't really recall).

The 4:1 switch is really a lot more convenient to use, and wedging 3 2:1 switches onto the board will be challenging

Please Log in or Create an account to join the conversation.

More
22 Feb 2015 17:46 #29005 by SadSack
Replied by SadSack on topic Single-Board Universal Module
Hi and welcome back :-)
Could 4:1 switch + amp be moved to a daughter board?

Please Log in or Create an account to join the conversation.

More
22 Feb 2015 18:41 #29007 by victzh
Replied by victzh on topic Single-Board Universal Module
Remind me, did you insert the blocking cap between switch output and PA/LNA input? The schematics does not have it, and these things can be sensitive to DC component. SKY13384 datasheet recommends 100pF blocking caps on all inputs/output, and while all inputs seems to not have DC connection, the output can.

Please Log in or Create an account to join the conversation.

More
22 Feb 2015 18:42 #29008 by mikemacwillie
Replied by mikemacwillie on topic Single-Board Universal Module
Yeah, I've got the blocking cap between the switch and the PA/LNA.

Please Log in or Create an account to join the conversation.

More
22 Feb 2015 22:49 #29024 by PhracturedBlue
Replied by PhracturedBlue on topic Single-Board Universal Module
I worked on the board a little today, and was able to replace the 4:1 switch with 3 2:1 switches. It is more of a proof of concept at the moment, I'd really like to figure out why the 4:1 doesn't work 1st, but at least I know it can be done without a whole-board rework.

Please Log in or Create an account to join the conversation.

More
24 Feb 2015 01:17 #29065 by mikemacwillie
Replied by mikemacwillie on topic Single-Board Universal Module
That's good news that it'll fit. I haven't really had a chance to dig into why the current switch isn't working yet.. But I will soon. There is a drop-in replacement available from Hittite as well, but it's super expensive relative to the Skyworks. Which 2:1 switches were you looking at? I've used a couple of the Peregrine switches in the past with good luck.

Please Log in or Create an account to join the conversation.

More
24 Feb 2015 05:03 #29070 by PhracturedBlue
Replied by PhracturedBlue on topic Single-Board Universal Module

mikemacwillie wrote: That's good news that it'll fit. I haven't really had a chance to dig into why the current switch isn't working yet.. But I will soon. There is a drop-in replacement available from Hittite as well, but it's super expensive relative to the Skyworks. Which 2:1 switches were you looking at? I've used a couple of the Peregrine switches in the past with good luck.

i started looking at chips that are on boards i have but most use 2-wire Control signaling. So i designed them with peregrine chips which are single wire. I'm using the 42421which i think is the same as the 4259. I can't figure out the difference between the two. I can't meet the recommendations for the transmission line, 0.5 pf caps on the output. If you have experience, maybe you can look over my design and see what you think.

Please Log in or Create an account to join the conversation.

More
27 Feb 2015 16:22 - 27 Feb 2015 16:35 #29165 by moss
Replied by moss on topic Single-Board Universal Module
WB PB!
The only difference I can see between the PE42421 and PE4259 specs is the advertised ESD tolerance, on the front page.

I'm using the 4-way PE42641MLBC-Z with no problems, for another project. These do not require DC blocking caps, unless you put DC on them. Pin-outs are also quite similar but different, but the same general layout would work. The truth table are also different for RF2 and RF3.
Using 3 SPDT switches seems more difficult than necessary.
The control lines should be bypassed with some caps, besides RF-leakage will get into the signal here (not a problem for a TX), the max switch rate is 25 KHz and limiting the bandwidth to keep RF out of these points can't hurt. In your setup the switch rate is super low so caps her could keep you out of trouble.

Neither PE nor SKY advertise RF isolation to control and DC lines.
Last edit: 27 Feb 2015 16:35 by moss.

Please Log in or Create an account to join the conversation.

More
27 Feb 2015 17:20 #29168 by midelic
Replied by midelic on topic Single-Board Universal Module
which RF switch did you use before?

Skyworks SKY13384?

Please Log in or Create an account to join the conversation.

More
27 Feb 2015 18:10 #29169 by moss
Replied by moss on topic Single-Board Universal Module
SKY13384-350LF

Please Log in or Create an account to join the conversation.

More
27 Feb 2015 18:29 - 27 Feb 2015 18:34 #29171 by midelic
Replied by midelic on topic Single-Board Universal Module
Not sure if this was the problem...but on this chip you have the single antenna input and 4 RF outputs.
In a transmitter should be the other way around,...4 inputs and one output.
This signal is unidirectional from Antenna pin to each output pin...not opposite.
So I think it will work for receiving but not for transmitting.
Last edit: 27 Feb 2015 18:34 by midelic.

Please Log in or Create an account to join the conversation.

More
27 Feb 2015 18:35 #29172 by moss
Replied by moss on topic Single-Board Universal Module
the switch does not "know" how the RF signal passed thru it is used, it just conducts, or not.

Please Log in or Create an account to join the conversation.

More
27 Feb 2015 18:39 #29173 by midelic
Replied by midelic on topic Single-Board Universal Module
How do you know that?In the data sheet it is not specified that...... but is specified clearly that antenna input and the other 4RF pins as outputs.I think it should be specified if is bidirectional.

Please Log in or Create an account to join the conversation.

More
27 Feb 2015 19:16 #29174 by PhracturedBlue
Replied by PhracturedBlue on topic Single-Board Universal Module
The Description of the Sky13384 says:
"The SKY13384-350LF is a symmetrical, single-pole, four-throw (SP4T) switch"

'symmetrical' here means bi-directional. Still doesn't explain why it doesn't work though.

Please Log in or Create an account to join the conversation.

More
27 Feb 2015 19:25 #29175 by midelic
Replied by midelic on topic Single-Board Universal Module
Actually I don't think is true,
Symetrical in RF world means the input and output have equal impedance,..in this case 50ohms.
I think the chip is unidirectional and for this reason not working.

Please Log in or Create an account to join the conversation.

More
27 Feb 2015 19:46 #29176 by hexfet
Replied by hexfet on topic Single-Board Universal Module
The note below in the datasheet seemed unusual to me. Does it also imply the RF inputs should not be driven when changing the control inputs?

The recommended startup sequence is:
Step 1: Apply VDD
Step 2: Apply VC1 and VC2
Step 3: Apply RF input
The device must be turned off in the reverse order

Please Log in or Create an account to join the conversation.

More
27 Feb 2015 20:32 #29177 by PhracturedBlue
Replied by PhracturedBlue on topic Single-Board Universal Module

midelic wrote: Actually I don't think is true,
Symetrical in RF world means the input and output have equal impedance,..in this case 50ohms.
I think the chip is unidirectional and for this reason not working.

Fair enough. I am not an expert in RF design for sure.

Please Log in or Create an account to join the conversation.

Time to create page: 0.111 seconds
Powered by Kunena Forum