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How to use boolean to control switch with fixed point data.

Asked by Joshua Wright on 15 Apr 2019
Latest activity Commented on by Joshua Wright on 17 Apr 2019
I am trying to use a boolean output from inside of Matlab function block to control a switch, which has 16-bit fixed point data. However, I keep getting the following error:
This assignment writes a 'logical' value into a 'double' type. Code generation does not support changing types through assignment. Check preceding assignments or input type specifications for type mismatches. Function 'FSM' (#1424.358.366), line 20, column 13: "path_sel" Launch diagnostic report.
It appears to force my output into a double type and fails. I noticed if I leave the switch data inputs open (floating) it runs fine and interprets the switch states as T and F.
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R2018b

2 Answers

Answer by Fangjun Jiang on 15 Apr 2019

You set the criteria of the Switch block as u2>=1, which implies that u2 is double data type. Through back propagation, it requies "path_sel" to be double.
Just change the criteria of the Switch block to be "u2~=0"

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Thank you for the suggestion. I updated the criteria as suggested but receieve the same errors and double propagation as before.
check the z delay block to see if somewhere "double" is specified. It should output a 'boolean' just as "fftlk_valid".
Did not see any speicification on the delay unit. I tried removing the delay and directly connecting but had the same errors.

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Answer by Bharath Venkataraman on 17 Apr 2019

S1 and S2 when they are assigned to mealy_state_reg likely need to be fixed point.
Try using assignements as follows:
mealy_state_reg(:) = S1;
mealy_state_reg(:) = S2;

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I added a convert block to ufix1 and that resolved the issue.

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