MSP-EXP430F5529LP: Issue with SBW-RST?

Jerry Gorman

Part Number: MSP-EXP430F5529LP
Other Parts Discussed in Thread: MSP430F5528, , TXB0104, TXS0102, MSP-ISO

I’m using a MSP430F5529LP as a status monitor for my other electronics. I have built a board to interface my electronics to the launch pad much like a boosterpack board. This board is powered and provides 3.3 volts to the MSP430 with the 3.3V jumper removed on the launch pad. This is done because I will not normally connect the launch pad to a USB port. The MSP430 does not run because it seems the SBW-RST jumper must be removed. If I do that my code on the MSP430 starts and runs fine. Only issue is that I want to retain the ability to connect the USB and update my code running on the MSP430 which does not seem possible if the SBW-RST connection is missing. Do I need to connect a FET where the SBW-RST jumper goes and have it switch on when the USB cable gets connected or am I missing something.

Thanks for you help.

Some general information about what I’m using on the MSP430

I2C to talk to an LCD display and read temps sensors, ADC channels to read system power supply voltages and GIPO to read status bits from other boards and control power up down sequencing.

over 3 years ago

0 Chester Gillon over 3 years ago

Guru 92251 points

Jerry Gorman said:
This board is powered and provides 3.3 volts to the MSP430 with the 3.3V jumper removed on the launch pad. This is done because I will not normally connect the launch pad to a USB port. The MSP430 does not run because it seems the SBW-RST jumper must be removed.

It sounds like the issue occurs when the ez-FET isn't powered, but is still connected to the MSP430.

Under that condition the un-powered ez-FET could be loading the SBW-RST signal on the MSP430, possibly holding it "low" and thus holding the MSP430 in reset. On the MSP-EXP430F5529LP the SBW-RST signal is directly connected to the MSP430F5528 on the ez-FET, and so when the ez-FET isn't powered the MSP430 will be trying to power the MSP430F5528 on the ez-FET via the SBW-RST signal.

Jerry Gorman said:
Do I need to connect a FET where the SBW-RST jumper goes and have it switch on when the USB cable gets connected or am I missing something.

That would would need to allow for the SBW-RST signal being di-directional when SBW is used to update the code. Maybe a bi-directional level shifter such as the TXS0102 or TXB0104 could be used instead, with the 'A' side connected to the SBW-RST.

The MSP-ISO would have been a simpler option, but the pinout of the MSP-EXP430F5529LP isn't compatible with the pinout of the MSP-ISO.