TMS320F28335: Serial communication not happening unless debugger is connected

Akhil,

Could you please erase the flash and reprogram it again? Also, on you board check the VDD3VFL pin (3.3-V Flash Core Power Pin). This pin should be connected to 3.3 V at all times.

I hope this helps. If this answers your question, please click the green "Verified Answer" button. Thanks.

- Ken

Hello ken,



I erased and flashed the code again but it didn't work. I checked the voltage level and it is working fine. And i think so that the code is flashed because the control system seems to be working fine. However, the serial communication is working only when i connect the JTAG.





Thanks,

Akhil

Akhil,

Could you please let me know what development tool (if not your own target) you are using? Is it an Experimenter's Kit?

- Ken

Hello Ken,


I am using TMS320F28335 microcontroller and it is not a experimenter's kit, we have made our own pcb.

Akhil,

Could you please let me know how your system is set up, such as what is the F28335 connected to? Could you let me know if you are using the emulator’s second channel to talk to a PC? That would certainly cause this behavior. Thanks.

- Ken

Ken,

               Do you want me to send the schematics? This was working perfectly fine like a week ago. This problem started to happen just now only.

Akhil,

You can send the schematics and I will have them reviewed. I just want to double check if you are using the emulator’s second channel to talk to a PC, as this would cause this behavior.

- Ken

Akhil,

This is looking more like a hardware related issue. Please check R24 near the JTAG header and make sure that it is populated on your board. The ideally value for this resistor should be approximately 2.2k ohms.

As for the ADM3215 isolation transceiver, the only concern is the F28335-facing signaling is expected to be to 5V IOs. When the SCI is transmitting, the device specification for logic high is 3.3V and this may not be adequate to drive the output. Also, when the SCI is receiving, the GPIO is likely exposed to 5V, which could stress the device and eventually cause it to fail. This may not be an issue here now, but you should consider fixing this to prevent long term reliability issues.

The XRSn is not being pulled high by an external resister. You should consider fixing this, too.

I hope this helps. If this answers your question, please click the green "Verified Answer" button. Thanks.

- Ken