RE: Propellar Chip Resets Itself when USB cable is removed

schwiegjc

When I run my Propellar program from EEPROM with the USB cable removed, the program will run for a·couple·of seconds then reset itself. This will repeat itself. I thought I read that there had to be a delay?·

Erik Friesen

If you are using fullduplexserial you need to disable the tx line if it is not connected to the usb. It will cause the ftdi to reset the prop.

schwiegjc

Is that a piece of software code or switch on the Propellar Demo Board??

Mike Green

The problem is that the USB chip is not powered (because it's not connected to a USB port) and, if your program attempts to transmit to the programming port or otherwise makes that pin a high output, the signal supplies enough power to the USB chip that it can accidentally reset the Propeller. The solution is to not try to use the programming port transmit line (pin 31?) unless it's connected to a USB port.

schwiegjc

The program that I am writing captures an ASCII data stream (Baud of 4800). To use the
BS2.Serin_Wait(COMPASS_RX,@DataIn,"T",4800,1,8) command, the BS2.BS2_Start (30,31) command has to be sent first. Do you think that is why the Propellar will reset itself if the Propellar USB port is not attach to the PC?

Mike Green

Yes

You could put a "dira[noparse][[/noparse]31]~" right after the call to BS2_Start. This will change the transmit pin back to input mode so it can affect the USB chip for only a millisecond or so.

schwiegjc

Thank you. Inserting dira[noparse][[/noparse]31]~ after the BS2_Start(30,31) resolved the problem.