How to send 4 bit data from NI8452?

Hello,

I want to send (0xAFF adress + 48bits data) sequence over SPI using NI8452 from Matlab. The write function of SPI object sends unit8 data, which converts above data into (0x0AFF + 48bit data), which changes the functionality of the next connected device.

I looked for the CS pin accessibility from code, so that CS can be enabled after 4 CLK cycles. But, I dont find any control over CS pin in Matlab.

Please let me know how I can code to send (0xAFF adress + 48bits data) sequence.

Answer 1

[Walter Roberson]

https://www.mathworks.com/matlabcentral/answers/346770-data-truncation-to-4-word-lengths-when-using-the-spi-transmit-block-in-the-ti-c2000-support-package implies that the device works in 8 bit multiples,

https://www.mathworks.com/help/matlab/supportpkg/analog-input-using-spi.html implies that you pad out to byte multiples if the device uses something that is not a multiple of 8 bits.

[Pratik]

Thank you Walter for quick reply.

I have gone throught the links. But, the device which I am connecting with strickly works on the (0xAFF address + 48bits data) data frame. I tried to club the data in 0xabc format. But, the data sent is supporting unit8 format, which value maximize to FF. Please check the trailing code which I have used,

Final_Seq = '00500294a5294a5';
Seq_1 = reshape(Final_Seq,[3,length(Final_Seq)/3])';
Seq_2 = strcat('0x',Seq_1);
hex_seq = str2num(Seq_2)

hex_seq = 5×1

5 2 2378 1321 1189

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dataToWrite = uint8(hex_seq)

dataToWrite = 5×1

5 2 255 255 255

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data_read = writeAndRead(Obj,dataToWrite); 

Unrecognized function or variable 'Obj'.

Please check and let me know if any solution is possible.

Thank you.

[Walter Roberson]

You should be considering using

typecast(hex_seq, 'uint8')

However, the result will be 10 bytes, which is not going to fit the 64 bit buffer.

I do not understand the connection between "0xAFF address + 48bits data" and what you are constructing ?

[Pratik]

Thank you Walter for the reply.

I am driving an BF-IC having SPI control. The data to be sent for commanding is (2bit preamble + 10bit address + 48bit word). Hence, the requirment is to generate such bit stream.

Please let me know any solution to generate such bit stream using NI-8452.

Thank you.

[Walter Roberson]

data64 = uint64(Preamble) * 2^62 + uint64(Address)*2^52 + uint64(Word);
data8 = typecast(data64, 'uint8');

Now transmit data8. The individual parts of it are each 8 bit integers and so will have no problem with the SPI.