Questions asked to producers of OBC

Question:

Just to confirm: if WDGSEL jumper is not connected, MCU pin is connected to WDI pin on watchdog? About lost boot index, we used following sequence:

1. Power up OBC
2. Set boot index to SourceDebug
3. Boot
4. Start watchdog test
5. Wait for MCU to restart
6. We expected that SourceDebug application will be booted again, however we got ‘Invalid boot index’ error

Answer:

"Yes, the MCU is connected to the WDI pin on the watchdog.

The bootloader index is stored in flash. If the boot loader reports that the boot index is invalid it means that the boot index is not in the valid value range. This can be cause by running the EBI test in the Source Application. This test basically overwrites the entire flash with test values. This also causes an invalid number to be written to the area where the boot index is stored. When the bootloader reads this invalid value it will report that the boot index is not valid. "

Question:

Could you explain what the P500 jumper is actually doing? I mean, that the P500 jumper attaches a pull-up/down resistor to the WDI pin (TPS3824-33 watchdog). Is it true or not?

Question:

Another question is: the R510 resistor (which is unpopulated, photo in attachment) is responsible for what?

Answers:

"The header P500 and resistor R510 is connected in parallel with each other and performs the same task. Having both gives you the option to use the header or to permanently make the connection by soldering a link to the P500 pads.

What P500 and R510 do is connect a pull-down resistor (R500) to the WDI pin. By attaching a pull-down to the WDI pin will cause the watchdog timer to start running. The MCU GPIO pin will have to pull the WDI pin high within the timeout period to insure the watchdog does not reset the MCU.

In other words if you connect P500 or R510 your software must toggle the watchdog within the timeout period from power on, since the watchdog will become active at power on. If P500 and R510 is not connected the WDI and the GPIO pin on the MCU is not initialized it will not cause a reset event. Only when the GPIO is initialized and toggled will the watchdog become active"

Question

• about not described in documentation nReset pin

Answer:

"We do not make use of the nReset pin. We use the Reset pin instead. This reset pin of the Watchdog is not directly connected to the JTAG/SWD reset line. "