Hi~ I'm sorry because it usually does not use English writing in English, So there may be errors in English please forgive me.
Last year, I bought some nRF51 Development Kits for project develop, nRF51 Development Kit with the chip is nRF51422(QFACA1).
however, We encountered some problems when design the custom PCB for our product development.
1st I programming a simple FW code to nRF51 Development Kits, the fw programming can to set GPIO P21 and P22 are output mode, and control GPIO alternate function low/high continuous. We let the FW programming in nRF51 Development Kits and test GPIO function work properly.
2nd Programming the same FW in our design custom PCB.After Programming FW is complete, Beginning work correctly, but after some time the GPIO operation began exception. GPIO maybe stop alternate function low/high continuous ,both always keep high ,both always keep low no work or error GPIO voltage level(like figure).
we also check the SWDIO Pin waveform and find an anomaly in figure.
When th FW Programming ready and CPU Start Run, SWDIO voltage level should be keep high. But in figure can see the voltage is not stable.
This is custom PCB schematic..
PS.
(1)ANT1 & ANT2 we are 100% copy the nRF51 Development Kits circuit and layout and components using the same, so I think that maybe not the issue or cause.
(2) We check all the power voltage state AVDD=2.8V VDD=2.8V DCC=2.8V DEC2=1.66V DEC1=1.2V the same with nRF51 Development Kits, so I think power maybe not the issue or cause.
(3) Bad soldering I think not the issue or cause. I already try soldering 6 samples and use multimeter confirmed. I find it unlikely that 4 out of 5 chip samples are bad.
