Cannot Connect to STM32F405RGT6 on Breakout (ST-Link V2)

[honboxuan]

Posted on December 25, 2012 at 14:43

Hello all,

I created my own breakout board for the STM32F405RGT6, but I'm unable to connect to it via the ST Link V2. The error is ''No Target Connected''.I've tested this with an external 8Mhz crystal (with load capacitors) and without. All other pins are simple broken out. I've successfully connected to the STM32F4 Discovery using the exact same method.After some searching, I found that pulling the BOOT0 pin HIGH allows me to see if the device is working. Sending 0x7F at 9600bps 8E1 to USART3 returns inconsistent bytes (changes all the time). On all pins of USART1, there is no response. The same thing on the Discovery board returns the expected 0x79 (on the first try, something else on all others).This is the first time I've developed a breakout for STM32 devices, and it is possible I've missed a connection required for it to work. So far, it is simply VDD, VSS, PH0, PH1, BOOT0 connected.Any help will be appreciated! Thank you!Hon

[ken239955]

Posted on December 31, 2012 at 06:07

What decoupling capacitors do you have on the PCB?

[Tesla DeLorean]

Posted on December 31, 2012 at 16:00

Board makes sense, but the resolution/clarity/macro make it hard to see the marking and orientation of the STM32F4. Can you get a clearer shot, or perhaps mark where Pin 1 is?

[honboxuan]

Posted on December 31, 2012 at 16:32

Sure thing. It's attached. Thanks for all your time thus far!

When I was soldering the chip, I found the orientation a little confusing as well. Just in case I got it wrong, pin 1 is at the top left corner (left edge) with reference to the text on the chip. ________________ Attachments : Connections.jpg : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HtTi&d=%2Fa%2F0X0000000aQW%2FKPLH0y2e6jnPeImEEIvtMal.94O_BCR2.1BUxEQdbTE&asPdf=false

[ken239955]

Posted on December 31, 2012 at 18:41 How do you know that is pin 1? Once I soldered a Freescale DSP56F807 incorrectly because their logo was oriented 90 degrees to the dot. I don't know how sensitive the STM32 chips are but it is universally accepted that all decoupling caps must be as close as possible to the chip. You have violated this fundamental practice. My decoupling caps on VDD, VDDA, VREF, VCAP_1 and VCAP_2 are all SMD and are within 2mm of the pins and directly connected to a ground plane.

[ken239955]

Posted on December 31, 2012 at 18:53

I don't have my STM chips here with me but I bet 100% you have the chip oriented incorrectly.

The dot indicates pin-1. Don't go by the printed logo. From what I can see on the STM32F4 Discovery manual, the logo is turned 90 degrees, exactly what happened with my Freescale chip.

[honboxuan]

Posted on December 31, 2012 at 18:55

Thanks for replying. Normally the correct corner is identified by a dot, but in the case of this chip, there are 2 on top and 2 on the bottom (all four corners). In short, I don't really know. Is there a way I can find out for sure?

I do know the need for the caps to be close, unfortunately there's not much I can do for now. I've modified by board design to have all everything close by.If we aren't able to find any mistakes at all, I'll attempt to solder the caps directly onto the legs of the IC. If that fails, I'll have the new boards made.

[honboxuan]

Posted on December 31, 2012 at 19:27

Ken, you are right. I've managed to connect via ST-Link after changing the orientation. I have some errors with losing connection, occasionally internal command error. I also get errors about flash mass erase etc.

Thanks to all who helped, and sincere apologies about the thoroughly uninteresting mistake.

[ken239955]

Posted on December 31, 2012 at 20:20

Nice to know what is the problem. Next time you do a PCB layout plan on making the bottom side a full ground plane, perhaps with the occasional trace connected to the top side. I use copper pour to get the ground plane to wrap around all traces and pads. (I use Eagle PCB layout).

Use SMD 0.1uF capacitors on all supply lines and 2.2uF on VCAP_1 and VCAP_2. Give your decoupling capacitors and supply lines high priority, placing the caps as close to the chip as possible. Connect the GND side of the caps to the ground plane using a via right through the SMD ground pad.

[honboxuan]

Posted on December 31, 2012 at 20:41

I usually use 2 sided PCBs for stuff like this. It's quite difficult to break everything out without going to the bottom plane. Even though it's technically a ground pour at the bottom, it's quite badly cut up with all the traces.

Also, I'm getting quite a few errors with ST Link, like the ''Disable Read Out Protection...'' related stuff. I might just try moving the caps very close to the pins.

[Tesla DeLorean]

Posted on December 31, 2012 at 21:24

You look to have a bunch of SMT land patterns on the board, presumably for caps and a crystal.

Here's a 64pin F0 and F1 part, Pin 1 is marked with a red star