Radio Module fails to transmit data when PMM module is enable to monitor power supply in MSP430F6779A

Hello Dhara,

What radio module are you using?
How is the MSP controlling the radio Module?
Is the MSP resetting due to voltage drop when the radio is on? If so, does this reset force the MSP to reset the Radio?

With what little information that is given, it seems the MSP is resetting your radio, when the MSP gets reset due to voltage dip when radio is turned on. This would mean you need more decoupling between the MSP and Radio power supplies. Separate VCC rails for the MSP and the Radio would accomplish this. You could also try additional, larger decoupling caps added to the DVCC input of the MSP430.

Hello Jace H,

I am using Xbee as my radio module. I am trying to communicate data between have two end devices with Xbee. On one of the end device is MSP430F6779A connected on UART with Xbee. This device with MSP430 has to recieve and save the data (in flash on power off) which is communicated by the other end device (connected with my PC). The supply to MSP430 and Xbee is from same power rails and there are fair enough decap on their input pins.

I would brief the steps of my iteration:
First I am sending data from Xbee (connected with my PC) to the other device (with Xbee and MSP430). I am able to receive that data.
Then I turn off power of MSP430 board.
I turn on supply and I have to read from flash for the data that was received (and written to flash on power off).


I had iterated to read and write data in flash when supply is through debugger or through other power sources and its working perfectly.

When I connect Xbee and disable PMM module, Xbee communicates and I can recieve the data but still writting-reading from flash is still not working.

When I enable PMM module Xbee fails to communicates.

I hope I am able to explain my problem appropriately.

Please, let me know how can I over come this.

Thanks in advance.

Regards,

Dhara.

When I connect Xbee and disable PMM module, Xbee communicates and I can recieve the data but still writting-reading from flash is still not working.

When I enable PMM module Xbee fails to communicates.

Erasing and writing the Flash also increases the power draw considerably. Seems you Vcc drops below brown-out level under increased load - either because it's too weak, or improper impedance (non-optimal PCB design, insufficient decoupling capacities).

Use a scope to watch Vcc on the MCU and on the XBee module during a fail/reset, as close to the pins as possible, and keeping the wiring to the probes as short as possible.

Hello f. m. (3568074)

Thanks for the reply.

I tested the board and there seems to be no hardware issue. I connected decoupling capacitor of 100uF (25V) on DVcc pin of controller. I also checked the supply fall on the oscilloscope on DVcc pin of MSP430 and Xbee and observed that fall down occurs on same time in both devices.

Channel1 = DVcc of  MSP430F6779A 

Channel2 = DVcc of Xbee

Pls, let me know if there are any other ways to solve it.

Regards,

Dhara.

I also checked the supply fall on the oscilloscope on DVcc pin of MSP430 and Xbee and observed that fall down occurs on same time in both devices.

I see. Could it be that your power supply (3.3V regulator) has a kind of over-current detection, and turns off ? Looks suspiciously like a "normal" power-off.

Hello f. m.

Thanks for you reply..

Right now I am testing my module with MSPFET - 430UIF debugger supply.. I am not connecting any other power supply.


Regards,

Dhara.

Hello f. m. ,

We are operating two radio modules from same debugger supply simultaneously and it is able to transmit and receive data perfectly.

I doubt if theres any power issue..!!

Regards,

Dhara.

We are operating two radio modules from same debugger supply simultaneously and it is able to transmit and receive data perfectly.

While this might be an indicator, this is not a proof.

I doubt if theres any power issue..!!

Fine. But I am not sitting in from of your hardware - I don't even have such a MSP430F6779A board and radio module.

Be proactive an try to localize the problem - supply your MSP430 board from another, stable power supply. If the issue disappears, the debug probe caused the problem. If not, it could be power supply circuitry on the board, or something different.

Debugging such problems is a major skill in the engineering business.

Thanks f. m. for guidance and motivation..

I will try to localize the issue.. and will post the updates as soon as I debug the problem...

Regards,
Dhara