TXD, RXD data format

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1 
 As a school project i am developing a software interface(using BeagleBone Black and Python) to transmit data from TXD and RXD ports to and from a PC. 

 For starter i want to try the capabilities of the BBB transmitting a list of 12bits parallel word to TXD port in order to check its output, and i was wondering if the data recieved (or delivered) by these ports has an specific format, i mean: does it have reserved bits? is it signed? is it all positive, no negative part? I didnt find any document involving this subjects, if you could point me one i will be glad.

Thanks in advance. 

Jesus.
2

@Yeshua,
In the transceiver datasheet it’s specified that the ADC/ADCs require two’s complement format for the output/input 12bits. So I think bit 11 which is MSB is the sign bit.

3

For the Myriad RF which equates to using the LMS6002D the DAC’s and ADC are 12 bit 2’s complement as seen in TABLE 7 and TABLE 8 of the LMS6002D data sheet. The Most significant bit is the signed bit of course. Therefore if driving the TX dac the range should be from -2048(0x800) to +2047(0x7FF).
To do a simple test is to send a sine wave on the dac and then using the oscilloscope I would measure TXIN on X4 connector of the myriad. Note that it is a differential signal going to X4 connector.

Also note you need to turn on Hard TX Enable and the SOFT TX enable (Register 5). Also have to drive the TX IQ select.

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