evm5515 - spi interface

Hi,

I'm guessing that you are reading from cc2500 faster than cc2500 data feeding.You may have to slow down your SPI readings.

Regards,

Hyun

Since you are sending the STX command to start a transmission, the most likely reason for a TXFIFO_UNDERFLOW is due to not keeping up with the radio reading data from the fifo.  You will want to pre-charge the fifo by writing at least a few bytes to it before strobing the STX command.  Ideally, if you can fit your entire packet into the fifo then you won't have to deal with the timing issues of managing the fifo.

Jim Noxon

I'm feeding the TX fifo with 61 bytes and then sending the STX strobe.

the fifo size is 64 byte so I assume I don't have to deal with the timing issue.

if that's true, why do I still get the TX_UNDERFLOW state?

I read the status byte in a forever loop and the c2500 get stuck in TX_UNDERFLOW.

If you are in variable length packet mode you must write the length byte to the fifo first so the hardware knows how many bytes to send.  If you are not writing the length byte and the first byte is a value larger than the length of the packet, you will receive a TX_UNDERFLOW.  In this case you must issue an IDLE instruction to the radio state machine to reset it.

Jim Noxon

I do set the first transmiting byte with the packet length and still get into TX_UNDERFLOW state.

any idea why?

Are you including the length byte and the crc byte in the length calculation too?

Jim Noxon

I've found the problem . my packet length byte was wrong (I include the packet length byte and the address)

Thanks