baseboard serial receive fifo

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Gorkem 2016-7-23

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https://ww2.mathworks.cn/matlabcentral/answers/296906-baseboard-serial-receive-fifo

评论： Walter Roberson 2016-7-29

Hello,

I'm using baseboard serial fifo out block to receive data @ 1kHz from an external device.

The device sends a unique header byte at the beginning of each message packet.

However, message length isn't fixed. For that reason, I decided to use ordinary fifo read block instead of fifo bin read. So, I wrote my own state machine to sync with messages.

The fifo read block is configured as count + uint16 array.

even though it is working without any problem mostly, sometimes it gives some strange values.

for example,

4 39(header) byte1 byte2 checksumbyte is what I'm expecting.

But fifo read block sometime gives me something like : 4 <some integer above 255> byte1 byte 2 checksumbyte or 4 39 <some integer above 255> byte 2

what does that mean when an element of fifo read is greater than 255? Simple decomposition of that uint16 value into two uint8 values just gives some random numbers.

Any help is appreciated.

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Gorkem 2016-7-24

编辑：Gorkem 2016-7-24

在 MATLAB Online 中打开

Thanks for quick response.

next to header, there are two data bytes and the last byte is checksum.

for example : the first line has two data bytes as 253 and 97, which is to be evaluated in 2-s complement format as -671.

last line contains correct data as well. when it's interpreted as int16, it corresponds to value -433.

data is a position measurement from an external device. so for the message packets between the first and last lines, data should take values between -671 and -433.

in uint8 array form, this would be something like 254 or 253 for the first byte and some value between 0 and 255.

As for the uint16, you have a good point, but the thing is external device, which is transmitting, is a digital sensor which is configured as having data of 8 bits length and my serial board configuration is so as well.

EDIT:

Sorry I missed your question. There are 5 rows coming out wrong, which are 2 3 4 5 6

for row 2,4 and 5, checksum is wrong. for other rows among wrongs, I am not sure how to calculate checksum since they contain some bytes of 16 bits. However, if I do direct calculation, they seem to be wrong as well.

Gorkem 2016-7-25