swd programming and 3.3v power ???

[xavier2399]

Posted on January 26, 2013 at 16:19

Hi all,

I've had great difficulties setting up my own STM32F405 board and having it actually run, but finally I've succeeded booting it and programming it from my stm32f4Discovery. However I have a very strange behaviour : If I power my board using USB+LM1117 3.3v regulator (seems mostly clean/accurate  on scope), if I try to program it with STLinkv2 interface (from discovery board) the connexion fails. a scope on swd clock seems to indicate that the clock starts to oscillate and then stops. It won't program the chip but once programmed, the program will run on that power source with the right clocks, VBats & all. If I power my board using batteries (3x1.2v before regulator) and connect it to st-link from discovery, it fails, then if I try again I can program it. Then everything runs OK. If I leave the probe on the Vcc pin of swd, it seems that power goes from 3.3v to 3.6v when powered from usb, and from 3 to 3.3 when powered from batteries : what gives ? Strangest thing, if I leave the probe, the device seems to run OK and program OK even with USB ! If I remove the (passive, tektro, 1Mohm) probe, I cannot program until I go to battery power. I recall having see a thread (by bil.til?) where the conclusion of swd link ability to communicate  was to step down the power of the chip from 3.3v to 3v but I can't find it (bad forum software). Can anyone enlighten me ? Besides I have a somewhat related question. If you pull up Boot0 to 3.3v, does the chip consider that VPP is pulled high (albeit not at 9v) - because it's the same pin ? does the fact that VPP must only be applied for 1 hour of the life of the chip means that Boot0 must be pulled up for 1 hour for the life of the chip ? #power-stm32f405-swd-vpp

[glory_man]

Posted on October 03, 2013 at 15:07

Did you solve your problem?

I also have strange problems with self-created board based on stm32f407. I try to programm board via swd from stm32f4discovery. Sometimes my board erased,  somitemes none.

[Tesla DeLorean]

Posted on October 03, 2013 at 15:43

Connected how exactly, do you have NRST? I wouldn't connect the supply, just the common ground.

To the earlier VPP question, the One Hour relates to pushing the 7-9V in Make sure you have ALL the supplies connected up, and that VCAP pins have their capacitors. ST should have just stuck with the standard ARM 10-pin header instead of inventing 4/5-pin headers. When designing ones own boards standard headers/connects are recommend.

[zhenya_rai]

Posted on October 04, 2013 at 16:59

Power supply 3.3V at the own board. Connection own board with stm32f4 discovery at the picture.

________________ Attachments : stm32f407.jpg : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006I0er&d=%2Fa%2F0X0000000bc4%2FuPoKLpCXd15rQEoRvLlNLJ0kExLlsoxLloHvVxaPfq0&asPdf=false

[zhenya_rai]

Posted on October 04, 2013 at 17:03

I'm about glory man post.

[Tesla DeLorean]

Posted on October 04, 2013 at 17:44

Figured

Quick scan suggests the right pins. You have caps on VCAP1/2 pins, and can measure ~1.25V? Make sure you unsolder SB12 (SWO) on the STM32F4-Discovery so you don't get pins fighting on PB3 (133) I'd be tempted to look at SB11 (NRST) too. I've tended to prefer stand-alone JTAG/SWD I'll look it over some more later.