Home soldering

[TestSubject06]

Well, I almost managed to join you guys. when I plug in the fpga board, I get no response from the board. The voltages on the regulators seem to be fine, it just doesn't enumerate. There are two possibilities I can see:
1. The LX9 FPGA is ever so slightly off-center on two sides. I can't tell any signs of obvious awfulness, but there's a good chance it could be bridging at random spots.
2. the M25P40 set that I got decided that it wasn't important to mark any corners, so I took a bit of a gamble and assumed that I should be able to read both the silkscreen and the chip without it being upside down.

Given both of these, am I going to have to scrap everything and build a new one, or should I be able to turn aruond the little chip / maybe somehow reseat the lx9?

[prophet36]

The voltages on the regulators seem to be fine, it just doesn't enumerate

It's the FX2 that should enumerate, not the LX9. So the first thing to do is check the orientation and soldering of that chip; I use a USB microscope and a needle to poke each leg in turn to make sure it's soldered down. If that's OK, the next step is to verify that you've soldered the D+ and D- pins correctly on the USB socket, again with a microscope. The USB socket is IMHO the hardest component to solder, which just seems wrong but there you go. Next, check that you soldered on the correct resistor and capacitor values for the FX2's reset circuit, the two pull-up resistors on the SDA and SCL pins, the orientation of the FX2's EEPROM and the the value of the 24MHz crystal oscillator and its two capacitors.

Edit: another common problem when using liquid flux is that it gets into the USB socket and insulates the conductors. Wash it thoroughly with methylated spirit or surgical alcohol and a toothbrush, and try plugging the USB cable in and out repeatedly (with the other end of the cable disconnected) to scrape off any gunk that might be left inside.

there's a good chance it could be bridging at random spots

You need to be able to state conclusively whether there is or is not bridging. Hoping for the best is probably not the way to go. Try the USB microscope & needle approach I mentioned.

If it makes you feel any better, when I tried soldering my first LX9 boards I ruined several PCBs and FPGAs before I managed to get the technique right.

[TestSubject06]

Welp. Wrecked everything. Waiting on some new components to ship out to me.

Is there anything I can check to verify the bridge board without the fpga board being done?

[prophet36]

Welp. Wrecked everything. Waiting on some new components to ship out to me.

What happened?

Is there anything I can check to verify the bridge board without the fpga board being done?

I guess you could wire it up to a +5V and +3.3V supply and feed a +5V square-wave into each address-bus signal in turn on the MD side and verify with an oscilloscope that you get a +3.3V square-wave on the corresponding pin on the LX9 side. The bridge-board is (you're probably already aware) considerably simpler than the LX9; I would've thought it would be tricky to mess it up.

[TestSubject06]

What happened?

I tried to take off the chip that was on backwards (I noticed it smoking when it was plugged into the USB port) and a few pads lifted off... Then I tried to salvage the lx9 and a leg popped off. I never did get the FX2 to enumerate. All of the joints looked and felt good with some prodding, as did the USB port. The tantalum caps are the only ones where direction matters, right? (for caps and resistors).

Anyways, got a new lx9, sdram, and fx2 on the way. I have enough of the rest of the parts to get the board mostly ready while I wait.

With the flash memory chip, how do I know what orientation it should go if it doesn't have the corner marked?

[Montserrat]

Welp. Wrecked everything. Waiting on some new components to ship out to me.

Is there anything I can check to verify the bridge board without the fpga board being done?

If you gather 4 more people you can order a 5x run of UMDK kits for 170$/unit shipping included. We had good results.

[prophet36]

I split this out into a separate thread, because it's unrelated to Montserrat's software set-up & debugging post.

Anyways, got a new lx9, sdram, and fx2 on the way. I have enough of the rest of the parts to get the board mostly ready while I wait.

If you prefer, you can solder the components in stages. This should be enough to get the FX2 to enumerate:

• REG3.3, C9, C10, J2, J3 & J4.
• CONN3 & XTAL1.
• U2, R2, C1, C2, C3, R5, R6, C13 & C14.

Then you can add the EEPROM to get the FPGALink/FX2 firmware-load to work: U4, C8, R4 & J1.

Next you can solder the FPGA and its decoupling caps & its resistor. This should allow you to do the JTAG scan-chain, and program the FPGA with cksum.xsvf, and run the checksum test:

• U1.
• REG1.2, C11 & C12.
• R9, C15-29.

Next the flash. This should allow you to run the flash tests, and boot the FPGA by loading cksum.bin: U5, R1, C31.

Next the SDRAM. This should allow you to do the SDRAM readback test: U3, C4, C5.

Next, the 80W edge-connector: this should allow you to do the basic MegaDrive tests and boot the UMDK production firmware.

Finally the SD-card slot. This should allow the menu program to proceed from the UMDK splash-screen and present the menu of ROMs to load: CONN1, C6, C7 & R10.

With the flash memory chip, how do I know what orientation it should go if it doesn't have the corner marked?

My batch of flash chips are oriented like this:



It tells you in the datasheet where to find pin 1: one of the long edges on the top of the chip has a slight bevel edge, indicated by my mouse-pointer on the diagram below. If you orient the chip so that bevelled edge is at the bottom, then pin 1 is the pin in the bottom-left corner.

[TestSubject06]

Oh wow, that's some awesome information.

I didn't know about the bevel on the flash chip. And I'm glad that I'll be able to test the board piece by piece as its put together.

[TestSubject06]

Reg3.3 xtal connect j2 j3 j4 c9 c10 c1 c2 c3 r2 r5 r6 and u2 are on and clean, no pins wiggling on anything

Time to see if this enumerates.

We have enumeration! Though I may well have had enumeration before, I had to look in /var/log/kern.log on xububtu, and even then I had to cat grep to find the Damm thing, but it's there! 04b4:8613

Tomorrow I'll move on to phase 2.

[MintyTheCat]

We have enumeration! Though I may well have had enumeration before, I had to look in /var/log/kern.log on xububtu, and even then I had to cat grep to find the Damm thing, but it's there! 04b4:8613

lsusb command should do the job.

[TestSubject06]

lsusb command should do the job.

It would, if it didn't hang. I don't know why it hangs. I hope nothing else hangs.

[MintyTheCat]

lsusb command should do the job.

It would, if it didn't hang. I don't know why it hangs. I hope nothing else hangs.

Does it hang only when you plug UMDK into your PC?

[TestSubject06]

Well I didn't try before it was plugged in, but after it had been unplugged and for a while it was still hanging. I didn't have time to do a full reboot and try again, and I'm going out of town tonight, so it'll be a little while before I can try again / move forward.

[MintyTheCat]

Well I didn't try before it was plugged in, but after it had been unplugged and for a while it was still hanging. I didn't have time to do a full reboot and try again, and I'm going out of town tonight, so it'll be a little while before I can try again / move forward.

No need to do a reboot: simply unplug UMDK from the PC then do an lsusb:

For example do the test before and after to see if it is UMDK that is causing the issue.

If lsusb hangs it should be possible for us to see this in a log file under Linux.
I do not know enough about USB to comment on why an issue would cause it to hang but perhaps it is possible to set a time-out for USB device enumeration, not sure.

[prophet36]

It would, if it didn't hang. I don't know why [lsusb] hangs. I hope nothing else hangs.

What do you see in /var/log/messages when you connect the LX9 board? What to you see when you subsequently disconnect it?

If you try lsusb on a fresh boot before connecting the LX9, does that hang? If not, what does it report?

If you run the lsusb in one window and the tail -f /var/log/messages in another window, do you see anything in the log at the point when lsusb hangs?

Can you try sudo strace lsusb and upload the last few hundred lines of output somewhere for me to look at (don't post it here, it will be unreadable).

Can you post a photo of both sides of your LX9 board, so I can see which components you've soldered so far?

With the LX9 board disconnected, can you get a multimeter and measure the resistance of R5 and R6?

With the LX9 board connected, what is the voltage at the output of REG3.3?