My USBDM is not stable

[wangbaode]

Hi pgo,

1,I made a USBDM for kinetis KL05. The hardware is USBDM_SWD_SER_JS16CWJ_V2.0.Because USBDM interface of SWD is Kinetis 20p .But my demo board SWD interface is Kinetis10pin.So I use a adapter bewteen knitis 10pin and kinetis 20pin and The adapter is USBDM_JM60.It can work like that.

The board in the picture is my adapter.

2,But When I remove adapter,I connect kinetis 20pin with kinetis 10pin.It can't work.

can you give me some suggestion?Is there other people to meet the question?

[pgo]

Hi Wang,

Is it possible that you are connecting the cables so that the connections are reflected?

In any case the simplest way to connect a 20pin BDM to a 10pin Target is to simply remove pins 11,12,13 & 14 on the BDM header.  Leave the header in place just remove those pins.  This should allow you to directly connect a 10pin cable and also allow the use of a 20pin cable since the removed pins are unused.

bye

[wangbaode]

Hi pgo,

It can't work when I connect VDD_BDM to 3.3V. But when I connect VDD_BDM to 5V ,it can work . kL05 device should work in 3.3v supply. so I'm confused very much.

[pgo]

Hi Wang,

I'm confused by your description - does it work at 3.3V but not at 5V or the other way around?

Anyway - are you using the specified TI 74LV125A chips?

bye

[wangbaode]

Hi pgo,

Thank you very much.I check my board and found that I use 74LVC125 to replace 74LV125A.I purchase 74lv125A chip and replace 74lvc125.My BDM works well.Thank you.

Best regards for you.

[pgo]

Hi Wang,

glad to hear that fixes it.

The 74LV125 are a bit special as they tolerate 5V on the outputs when operating from 3V.  LVC chip will often have feed through from the pin to the power rail.

bye