Serial port timeout- 10 seconds, but getting less samples than expected/desired

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want2know
want2know 2015-3-18
回答： Michael Du 2019-12-18
Dear Sir/Madam,
I have the following error while trying to access serial port data sent from Nios II UART: The specified amount of data was not returned within the Timeout period or A timeout occurred before the Terminator was reached.
The above error occurs when I set the timeout to be smaller than 10 seconds, say 2 seconds, or 6 or 8 etc.
set(s,'BaudRate',115200,'timeout',10); %timeout is in seconds.
If I set the timeout to be as '10' or larger, I did not get the timeout error, however, with this timeout, the sample rate is 0.067Hz and the total number of samples I can obtain is only 493 in 120 minutes which is far too less. In similar system with timeout set to 2 seconds, we can get 46253 samples in 120 minutes with sample rate= 5Hz. (this worked previously when no Nios system is used, just FPGA)
What I think: I am getting so less samples because the Matlab needs to wait longer now compared to previous system where no Nios is used.
What I dont know and need your opinion: how to increase the number of samples to be received? how to increase the sample rate?
What is in my system (in C Code) : In main, the main calls for function "uart_multiple", I have 12 sets of data to be sent to the serial port, each set of data has 10 elements ('n' represents 10 bytes, one element is ONE byte), so I transmit one set of data one by one.
I suspect this could be the cause of low sample rate, but I am not sure.
Do you think we can transmit all 12 sets at the same time to avoid this issue?
If it is, what should I do to transmit all 12 sets at the same time?
int main () { uart_multiple (&txdata1, n);
uart_multiple (&txdata2, n);
uart_multiple (&txdata3, n);
uart_multiple (&txdata4, n);
uart_multiple (&txdata5, n);
uart_multiple (&txdata6, n);
uart_multiple (&txdata7, n); uart_multiple (&txdata8, n);
uart_multiple (&txdata9, n);
uart_multiple (&txdata10, n);
uart_multiple (&txdata11, n);
uart_multiple (&txdata12, n);}
Thank you in advance

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回答（1 个）

Michael Du
Michael Du 2019-12-18
I have similar questions. Matlab seems to set an upper limit to the serial port timeout of ~20ms and the serial input size of 2kB. So there is an issue if one wants to use the serial port to transmit data larger than the specified size.

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