On Mon, Sep 10, 2012 at 7:25 PM, Xiaohui Liu <whu...@gmail.com> wrote:
> Thank you for your prompt and helpful reply. CIL. > > On Mon, Sep 10, 2012 at 1:25 AM, Eric Decker <cire...@gmail.com> wrote: > >> >> >> On Sun, Sep 9, 2012 at 9:39 PM, Xiaohui Liu <whu...@gmail.com> wrote: >> >>> Hello all, >>> >>> I have a few things uncertain about USART on TelosB. >>> >>> 1) This may be naive, but I'm really curious why USART is needed in the >>> first place. Why can't the CPU talk to, say, CC2420 directly since they are >>> wired >>> together<http://webs.cs.berkeley.edu/tos/hardware/telos/telos-revb-2004-09-27.pdf> >>> ? >>> >> >> Huh? Well take a look at the 1611 data sheet. The USART hardware >> provides various functions but not at the same time. The CPU talks to the >> CC2420 through the USART as SPI. >> >> Read the TI data sheet and the user manual. And look at the telosb >> schematic. >> > > From page 6 of the > datasheet<http://www.ti.com/lit/ds/symlink/msp430f1611.pdf> showing functional > block diagram of MSP430F16x, P3 and USART0 seem to be separated. > It doesn't really show them seperated. It does show that the USART modules are on the busses that talk to the I/O ports. It doesn't show any actual functionality just how the busses. One can't really read anything into the diagram. It is an overview but doesn't convey any functional details. Not intended to. That's fine. > But from the > schematic<http://webs.cs.berkeley.edu/tos/hardware/telos/telos-revb-2004-09-27.pdf>, > > I assume you are talking about pg 54-56 > P3.1 is used as SIMO signal when USART0 is configured as SPI mode. > Ah no not exactly. P3.1 is connected to the MODULE when P3SEL.1 is a 1. The module is USART0 and can be configured to be run as a UART, SPI, or I2C. It is very confusing. But it is what TI did. It is how they chose to multiplex the different functions onto a limited set of pins. So for P3.1 to be SIMO you have to connect P3.1 to the USART0 module (via P3SEL.1 = 1) and configure USART0 so it is running in SPI mode. Then and only then will P3.1 be SIMO0. If you are using USART0 in I2C mode P3.1 will be SDA (P3SEL.1 still has to be a 1). If USART0 is being used in UART mode I don't know what P3.1 will do if P3SEL.1 is set. It is unspecified. > Is this because in TelosB, USART0's SIMO pin is physically wired to P3.1? > has nothing to do with TelosB. It is the msp430f1611 spec. Please read the data sheet (msp430f1611 specifically) and the associated users guide, chapter 9 and chapter 14. See http://www.ti.com/product/msp430f1611 I don't mind helping but I do expect you to do your homework. :-) more below > >> >>> >>> 2) What components/devices/peripherals are communicating with CPU via >>> USART? Via which one (USART0 or USART1) and in which mode (UART, SPI, or >>> I2C)? >>> >> >> look at the schematic. >> >> > USART0 is connected to CC2420 in SPI or I2C mode. Its UART mode is not > used. > SPI only. The CC2420 is SPI only. > USART1 is connected to USB in UART mode. Its SPI mode is not used. > Essentially. The feed into the USB is simple digital serial, I beleive a 3.0 or 3.3V digital signal. Yep it is UART only. > >>> 3) Can USART0 and USART1 be used in parallel? >>> >> >> yes. look at the data sheet. >> >> >>> For instance, can a strobe be sent to CC2420 using USART0 while the RSSI >>> register on CC2420 is being read using USART1? >>> >> >> huh again. I beleive a strobe is a message sent to the CC2420 but may >> also use a directly wired pin. >> >> The cc2420 is wired via only one set of hardware so your suggestion is >> non-sensical. >> >> >>> >>> Your explanation will be highly appreciated. >>> >>> -Xiaohui Liu >>> >>> >>> _______________________________________________ >>> Tinyos-help mailing list >>> Tinyos-help@millennium.berkeley.edu >>> https://www.millennium.berkeley.edu/cgi-bin/mailman/listinfo/tinyos-help >>> >> >> >> >> -- >> Eric B. Decker >> Senior (over 50 :-) Researcher >> >> >> > > > -- > -Xiaohui Liu > -- Eric B. Decker Senior (over 50 :-) Researcher
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