UART Rx Issue on TWR-KW24D512

[pedroruizdiaz]

Hi, I'm trying to run the hello world demo app included in SDK_2.0_TWR-KW24D512, but I'm having problems to send characters from my PC to the board. The strange thing is that the board is printing characters on terminal. 

I have three boards but only one is having this problem, I've already updated the bootloader to MSD-DEBUG-TWR-MKW24D512_Pemicro_v118 version using the reset button procedure and nothing change.

Any idea what to do? Thanks!

[jc_pacheco]

If the exact same application works fine in 2 other boards and you verified that TX_UART1 and RX_UART1 are functional, then yes it may be a HW issue on the IC or the bus lines from the IC to the K20. You could get in contact with your local FAE for a HW analysis. 

Regarding the RX sensitivity, is this also in the same "bad" board? Perhaps it got damaged for some reason. Just to double check: Are you using the SMA connector or the Inverted-F antenna? (C17 -> F-Antenna ,  C18 -> SMA).

[karel_povalac]

Hello pedroruizdiaz‌,

It looks like a wrong jumper setting on the TWR board. Please check your J18 jumper settings. The TX and RX signals should be shorted for the pins 1-2 and 4-5.

[pedroruizdiaz]

Hello!, the jumper setting is fine, I've compared with the other two boards and looks equal.

I've found that the Tx function works well but the Rx function doesn't work in UART and in RF transmisions neither!, don't know if this two things are connected. I had to modify the source of the ConnectivityTest_MKW2x_v1.3 to verify this due to my imposibility to send orders to the board through UART. :smileyalert:

The other two boards works well but only this one is giving me problems. I'm starting to think that a major issue is happening.

[jc_pacheco]

Hello Pedro,

This could be a hardware issue with your board or with the K20 used to pass the UART signals to the MKW24. Can you confirm with an oscilloscope if the TX and RX signals are being sent/received correctly on UART1_TX (PTE0) and UART1_RX (PTE1). 

[pedroruizdiaz]

Hi Juan,

Sorry for my delay to reply in this thread, I connected a oscilloscope on pins UART1_TX (PTE0) and UART1_RX (PTE1) and they are sending and receiving signals pretty well, but the KW24D512 still doesn't receive commands from PC. Maybe there is an internal problem with the UART1 periferic in the chip?.

I modified the source-code of hello world demo app included in SDK_2.0_TWR-KW24D512 to use UART0 and it works fine (can receive characters from PC), so I will move on using this, but the problem with rx signals from RF is still there.

One thing that I discover is that the problematic board have a very weak RF signal to send packets (in comparission with the other two boards), so I have to put the sender very close [less than 1 meter] to the receiver to execute the ConnectivityTest_MKW2x_v1.3. But maybe the best way to face this problem is opening a new thread.