Cutting SB38 - Cut VDD to Arduino shield for 52840 dev board

akif007 gravatar image

asked 2017-11-14 03:51:58 +0100

I need 3.3V on my Arduino connector, I need to use the Arduino shield. I am measuring 3V on VDD line. According user guide, if I cut SB38 , VDD will be disconnected, I assume this means that I will see 3.3V if I cut SB38. I think I did cut it with a pin and in my magnifier, I dont see the dot between 2 half circles. However, voltage is still 3V !! (how am I supposed to cut the solder bridge anyway ?) Is my understanding correct ? should I see 3.3 V on VDD pin on the shield ? if yes, what am I doing wrong ? if no, how can I see 3.3V on arduino connector , this is needed for my sensor device. your help appreciated.

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As far as I can tell all cutting SB38 does is disconnect VDD and VIO so the pins on the arduino connection which are VIO will just be not powered at all. I don't see where it has anything at all to do with 3.3V

RK ( 2017-11-14 04:38:09 +0100 )editconvert to answer

take a look at

see figure 20 an 21. VDD can be 3.3V in Arduino signal . how are we supposed to get 3.3 V in Arduino shield if VDD (3V) pin cannot be changed ?

sanjose007 ( 2017-11-14 06:57:32 +0100 )editconvert to answer

It's hard to track VDD around that diagram. I'm pretty sure that breaking that solder bridge just disconnects the pins entirely from VDD and unconnects them because I see no other source for VIO. Why it's marked as 3v3 on the figure I don't know because the voltage regulator is only 3v on the board.

RK ( 2017-11-14 07:16:44 +0100 )editconvert to answer

I think you are wrong.. User guide claims that Arduino connections are supported. In order that to be true, VDD pin showed needs to be 3.3V, instead of 3 V.. How can we get 3.3V on Arduino ?

sanjose007 ( 2017-11-14 19:20:54 +0100 )editconvert to answer

The on-board regulator on the nrf52840-Preview DK is 3.0V.

You can get 3.3V VDD by connecting a USB cable to the nRF USB connector on the PDK. You can then use the on-chip regulator to get 3.3 V.

Run this code at the start of your main() function:

    while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}

    while (NRF_NVMC->READY == NVMC_READY_READY_Busy){}

This should give you VDD at 3.3V VDD.

Remember to set the "nRF power source" switch to USB. And you might also need to reset the board once for the new UICR configuration to take effect.

Sigurd ( 2017-11-15 00:22:33 +0100 )editconvert to answer

So we have to connect 2 micro USB cables then to use Arduino connector pins with the above change ?

sanjose007 ( 2017-11-18 01:10:33 +0100 )editconvert to answer