Single-Board Universal Module

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27 Sep 2014 15:26 #25829 by mikemacwillie
Replied by mikemacwillie on topic Single-Board Universal Module
Yeah well, do anything enough and it becomes 'quite easy'. My day job involves prototyping my designs almost weekly.

I should have some time to populate the back sides this evening. I'll upload the firmware and see what I get. Any chance the Linux upload tool you wrote will work for this too? Or do I need to use the ST specific DFuSE tool?

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27 Sep 2014 19:30 #25835 by PhracturedBlue
Replied by PhracturedBlue on topic Single-Board Universal Module
the java-based upload tool won't work in its current form. I'll fix it one of these days.
I think the generic linux-based dfu-util will work for this though. it should, since this is just a stock dfu upload without any of the walkera specific encryption.

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28 Sep 2014 04:58 - 28 Sep 2014 05:29 #25839 by mikemacwillie
Replied by mikemacwillie on topic Single-Board Universal Module
After populating the back side of the board, I now have power to ground shorts on both. Looking at the eagle files, it looks to be in the regulator pads. The tab is connected to VSS, when it should be connected to +3V3. It's a common mistake if you're used to working with 78xx regulators, and I've made it myself more than once. I'm going to lift the tabs on the boards and see if that removes the short. I'd bet that's the problem with the board you built a little while ago.


Edit: Yep, that did it. dfu-util recognizes it now.
Last edit: 28 Sep 2014 05:29 by mikemacwillie.

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28 Sep 2014 05:28 #25841 by octagon
Replied by octagon on topic Single-Board Universal Module
Keep a data sheet handy when making foot-prints! Mark-ups yellow high-lights, whatever, to keep it simple.
Thru-holes needed for the parts can be included in the foot-print, to make it easier no not forget.
Paste layer can be added to foot prints too.

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28 Sep 2014 05:32 #25842 by octagon
Replied by octagon on topic Single-Board Universal Module
Agreed, the area is not that busy.
The TH types should be just as easy to source, and thru-hole reflow is old hat. Hot-plate may not be good for this though.

Add two fiducials in opposite corners for SMT machine placement, which also helps in aligning stencil for hand pasting.

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28 Sep 2014 05:52 - 28 Sep 2014 05:53 #25843 by PhracturedBlue
Replied by PhracturedBlue on topic Single-Board Universal Module

mikemacwillie wrote: After populating the back side of the board, I now have power to ground shorts on both. Looking at the eagle files, it looks to be in the regulator pads. The tab is connected to VSS, when it should be connected to +3V3. It's a common mistake if you're used to working with 78xx regulators, and I've made it myself more than once. I'm going to lift the tabs on the boards and see if that removes the short. I'd bet that's the problem with the board you built a little while ago.


Edit: Yep, that did it. dfu-util recognizes it now.

Well crap. I'm glad I didn't build the last board before you discovered that. I'd be pulling my hair out. I'm going to try reinstalling the stm32 on my built board, maybe I can salvage it. I'm very curious whether you have any luck powering up the transceivers. With the xtals on the bottom of the board, it may be necessary to reduce the caps for them to get stable oscillation.
Last edit: 28 Sep 2014 05:53 by PhracturedBlue.

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28 Sep 2014 17:05 #25851 by mikemacwillie
Replied by mikemacwillie on topic Single-Board Universal Module
My USB-Serial adapter seems to have died. :( I'll grab a new one tomorrow and test it out.

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28 Sep 2014 19:44 - 28 Sep 2014 19:44 #25855 by PhracturedBlue
Replied by PhracturedBlue on topic Single-Board Universal Module
I reattached the stm32 and fixed the 5v regulator. For some reason even without the boot0 jumper installed, I'm getting 3.3V on the boot0 pin, and the mcu won't exit the bootloader. If I pull the boot0 pin low, the board boots up and I see on the PPM pin:
Power Up
NRF24L01: Not found
A7105: Found
CC2500: Not found
CYRF6936: Not found
Done
Which is the same thing SadSack was seeing. Now I'll start investigating whether the transceiver xtals are toggling or not, and we'll see where it goes from there.
Last edit: 28 Sep 2014 19:44 by PhracturedBlue.

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28 Sep 2014 20:10 #25857 by mikemacwillie
Replied by mikemacwillie on topic Single-Board Universal Module
I found another USB-TTL adapter in my parts bin, and I have the same result. I'm glad yours is alive now!

Measuring crystals in circuit is not fun.. It's pretty easy to stop them with the capacitance and load of a scope probe. I look forward to hearing what your findings. Unfortunately I don't have any more time this afternoon to look at mine.

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29 Sep 2014 03:32 - 29 Sep 2014 03:32 #25861 by PhracturedBlue
Replied by PhracturedBlue on topic Single-Board Universal Module
I should have added probe pads for the various csn lines.

I was able to verify that the A7105 and CC2500 xtals were oscillating. I couldn't see any activity on the other 2.

I then scraped the resist off the cc2500 csn pin and attached a probe. I could see spi working as expected but no signal on MISO. I was thinking that maybe one of the other transceivers was holding the MISO line high because it wasn't staring properly. I was considering cutting the MISO lines to the other oscillators. As I was writing up the report in this post, I started to explain why the A7105 would still work. That is because it uses 3-wire SPI instead of 4-wire SPI. And then I looked at the schematic...The A7105 has MISO tied to GIO1. I did that so that so that an external board could use 4-wire SPI which is a lot easier than switching between 3 and 4-wire. But I'd forgotten about it, and had never configured the software that way. which meant the A7105 was holding MISO high and preventing proper communication.
A 2 line fix, and check this out:
Power Up
A7105: Found
NRF24L01: Found
CC2500: Found
CYRF6936: Found
Done

So, we're in business :)
I have to start writing code to control the board now, but I don't have time tonight. Anyhow, This is a major milestone.

Mike, here is the new dfu file to ensure your board also works:
dl.dropboxusercontent.com/u/52854517/uni...altx_DOA_working.dfu

The changes are:
in universaltx.c, move A7105_Reset() to the top.
add this to A7105_Reset() (in a7105.c..It must be after the SetTxRxMode call):
    A7105_SetTxRxMode(TXRX_OFF);
--> A7105_WriteReg(0x0B, 0x00); //Put GPIO1 into high-z mode
Last edit: 29 Sep 2014 03:32 by PhracturedBlue.

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29 Sep 2014 03:39 #25862 by mikemacwillie
Replied by mikemacwillie on topic Single-Board Universal Module
Ahh, that makes sense! I'm glad yours is up and running. Both mine are now too. Exciting!


I was going to offer to send you one of mine, but it sounds like that's not necessary anymore now that yours is alive as well. :)

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29 Sep 2014 07:57 #25864 by SeByDocKy
Replied by SeByDocKy on topic Single-Board Universal Module
Just amazing ....... when miracle can come true :).
Glad to know that the hardware part is really on the right track now :)
Bravo to all of three....

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29 Sep 2014 13:42 #25867 by PhracturedBlue
Replied by PhracturedBlue on topic Single-Board Universal Module
So the next step is to measure the RF performance of the chips. I'll do that by hooking them up to an RF meter and sending a constant data stream and sweep the channel. I'll then do the same on the pre-built boards I have and compare the output. Since the meter hooks directly to the antenna port, there should be no worry about getting any interference from external 2.4GHz sources.

I haven't used the meter hooked up to a PC yet (for recording), so I have a bit of learning to do there.

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29 Sep 2014 14:40 #25868 by mikemacwillie
Replied by mikemacwillie on topic Single-Board Universal Module
Just for my own curiosity, which meter do you have?

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29 Sep 2014 15:33 #25871 by PhracturedBlue
Replied by PhracturedBlue on topic Single-Board Universal Module
I have an RFExplorer. I think I mentioned it earlier in this thread. Not exactly a serious spectrum analyzer, but I think its about as good as you can get anywhere near that price-point.

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29 Sep 2014 15:58 #25872 by mikemacwillie
Replied by mikemacwillie on topic Single-Board Universal Module
Definitely. They look pretty damn good given the cost. I've come very close to buying one more than once.

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29 Sep 2014 16:37 #25873 by PhracturedBlue
Replied by PhracturedBlue on topic Single-Board Universal Module
did you try adding a dc blocking cap between the mux and the PA? I haven't made that change (I'm doubtful in my ability to do so without botching it).
I'm just crossing my fingers it won't bite me.

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29 Sep 2014 17:28 #25874 by mikemacwillie
Replied by mikemacwillie on topic Single-Board Universal Module
Not yet, but only because I don't have the PAs on there yet. Looking at the trace, it's going to be a little tight getting an 0402 in there, but it should be doable.

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29 Sep 2014 18:23 #25875 by SadSack
Replied by SadSack on topic Single-Board Universal Module
you could always use copper foil to add new set of pads :-) or temp test points. Only need foil and white vinger and 6% hydrogen peroxide peroxide and salt ..

Excellent news .

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29 Sep 2014 20:07 #25879 by moss
Replied by moss on topic Single-Board Universal Module
scraping off the solder mask under microscope with an X-acto blade is not that hard, easy no, but not that bad. Once the mask is well scraped off, add some solder to the copper.
Then you just need to cut a gap in the scraped trace, and reflow on the cap over the gap. Adding "pads"? Not necessary.

Look at eBay for "10X-20X Boom Arm Widefield Stereo Microscope" and you can find a decent solder scope for under $200.

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