You're right - and you're not. It seems indeed not to have to do anything with breakpoints/debug mode. But it is no simple serial connection too (which is expected by most people reading about this backchannel uart). Well, the naming 'backchannel' already implies that it is not a plain simple UART thing.
I just looked into the schematics. The two port pins you mentioned are connected through two series resistors to the LaunchPads MSP430F1612 processor (UART1). These pins are usually used for the ROM bootstrap loader on most MSPs. The very same pins are on the 1612 side of the series resistor connected to the TIUSB chip too, which is a very weird setup. And they are connected to the TIUSB chips PORT pins, whose usage depends on the TIUSBs (special) firmware. THE TIUSB serial connection goes to the 1612 only. I guess that is why there is only a control and no data channel available for the second USB COM port. The port pins are control lines. I don't know whether the TIUSB baudrate can be changed or is fixed to 2400Bd 8N1 (no flow control in any case). My guess is that the G22/1612 connection is used for simulating/forwarding a bootstrap loader connection (which needs special timing on the reset/sbw pins to enter, which is difficult if not impossible to time over a direct USB connection) and the additional, parallel connection to the TIUSB is use to 'sniff' on this connection and misuse it as a simulated serial port connection. This requires that only one of them is active (TIUSB or 1612) and maybe requires special initialisation of the TIUSB through the USB connection. Little is known about this as long as the firmware of TIUSB and 1612 are kept secret. The G22 implementation of the back-channel uart is indeed a timer-based software usart, which makes the timer mostly unavailable for own projects. And with 2400Bd it is really slow too. But since the whole G2 series does not seem to have any hardware UARTs at all (some have SPI/I2C), a software UART is the only way for an asynchroneous connection. It's a good idea but I think it has been done rather clumsy. Well, what does one expect from a product which is sold cheaper than the single-chip costs of the included 1612 processor alone? JMGross ----- Ursprüngliche Nachricht ----- Von: Jesse Frey An: [email protected] Gesendet am: 28 Sep 2010 19:11:38 Betreff: Re: [Mspgcc-users] msp430 launchpad uart back-channel under Linux there are real RXD and TXD pins on the board though. I don't think that they have anything to do with breakpoints. plus it shows as an extra COM port under windows. the IAR back channel thing seems like something that could be done to any board. Jesse ------------------------------------------------------------------------------ Start uncovering the many advantages of virtual appliances and start using them to simplify application deployment and accelerate your shift to cloud computing. http://p.sf.net/sfu/novell-sfdev2dev _______________________________________________ Mspgcc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/mspgcc-users
