CC1101-1190 Ref Design - GDOx Usage

You need two GPIOs for asynchronous mode and you need two control signal to control CC1190. So you need some control signals from the MCU.

TER,

The daughter board (DB) I am designing based on the ref design will connect to a separate mother board (MB) via a 60 pin male connector.  To interface the DB with the SmartRF development system, I envision an adaptor board with a 60 pin female connector on one side.  On the other side of the adaptor board will be the P1 and P2 connectors from the ref design which will plug into the SmartRF board.  During development with the SmartRF, the DB will be on top, the adaptor board in the middle and the SmartRF board on the bottom.  In the product application, when the DB is connected to only the MB, the 4-wire SPI interface pins will not be used.  Is it possible to use one or more SPI pins to control the CC1190  when the DB is not connected to the SmartRF ?

I have never used the CC1190 part, but I assume that the PA_EN & LNA_EN pins cannot be hardwired to GND or VDD since their states need to continously change depending on whether the CC1190 is in the RX or TX mode.  Is this correct ? 

Obviously, I am trying to avoid adding additional circuitry to the ref design and would like to look at other ways of doing 1) asynch serial comm, 2) CC1190 mode control and 3) SmartRF interface from the existing ref design.

Thanks

Dave

When using the reference design together the TRXEB some of the MSP430 IOs are routed to the EB connectors to control the CC1190. 

The HGM pin on CC1190 normally will be hardwired to Vdd. PA_EN and LNA_EN controls the PA and LNA and have to be controlled either by CC1101 or a MCU. If you intend to use asynch serial mode you only need one IO for this making it possible to use the two others for controlling the CC1190. Note that GDO1 is shared with the SPI interface. 

TER,

Could you please explain exactly your idea about how to use only GDO1 for asynchr serial communication.  The Mother Board (MB) that I need to interface with has two pins, RXD & TDX.  In the CC1101 part spec (p,63/98, sec27.1) it only refers to using two I/O pins for asynch serial operation,  "In TX, the GDO0 pin is used for data input (TX data).  Data output (RX data) can be on GDO0, GDO1 or GDO2".  I was thinking that I needed to use GDO0 to receive data from the MB and either GDO1 or GDO2 for transmitting data to the MB.  How would you propose to use only a single pin (GDO1) to do asynch serial operation ?   Please be specific.  Incidently, I was only aware of the SmartRF04EB and not the TrxEB.  I will look into the TrxEB and determine if it is a better fit for my application.  Thanks.

I think that there are seperate LNA and PA control signals mainly to be able to shut down both sections for low power applications. I bet you can use one signal to control both, by using an inverter on the LNA enable line. You just would have a higher power usage because the LNA would be on when in receive mode or idle, instead of just during a recieve.

Thanks Tim, I had the same idea about possibly using an inverter and one line to control LNA_EN and PA_EN.  I was hoping to find a posting on the Forum from someone who actually tried this approach sucessfully.

My main question still relates to TER-TI Employee's response that "you only need one I/O line to implement asynch serial mode instead of two".  As I indicated earlier, I need to interface the CC1101 with a mother board with RXD and TXD connections.  Can someone clarify how asynch serial can be done on the CC1101 with only one I/O line instead of two.

What I was thinking was to use GDO0 for both RX and TX

TER,

Please provide a few more details,  For example, would you set the CC1101 to be in asynch serial RECEIVE to start and wait for a message from the master  then change to TRANSMIT ?  What type of h/w would you use to connect the one GDO0 pin to the two RDX and TDX pins of the master ?  Do you know of any TI design notes, ref designs or examples that I could follow ?  Thanks,  Dave

We have done some software examples (nopt yet released) for the TRXEB board with CC1120 where we use only one IO on the MSP430 for RX/TX. If CC1101 should start being in RX or TX depends on your protocol, not on if one or two GDO pins are used. The CC1101 has to be set in RX or TX either way.