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[Solved] Incorrect bit order Bitstring [message #1772971]

Tue, 19 September 2017 11:17

Eclipse User

Hi everyone,

I work on ITS project (European project on connected cars), and we want to run ITS test on Titan. To do this, I develop a System Adapter.

In this SA, I have a message (a CAM) which contain a exteriorLights set to 20.
When I print the message value I have :

exteriorLights: 20

This exteriorLight is define in a ASN.1 (from asn1c), so we have a Bit_string which is a structure which contain :
- uint8_t *buf; /* BIT STRING body */
- int size; /* Size of the above buffer (number of bytes)*/
- int bits_unused;/* Unused trailing bits in the last octet (0..7) */
- asn_struct_ctx_t _asn_ctx; /* Parsing across buffer boundaries */

but when I want to put this value in the test structure, in a Titan BITSTRING. I obtain this error :

Matching on port camPort .msgIn.cam.camParameters.lowFrequencyContainer.basicVehicleContainerLowFrequency.exteriorLights := '00000100'B with '??1*'B length (8) unmatched: Fi

Because, in the BITSTRING corresponding to Titan exteriorLight I have :

exteriorLights := '00000100'B

To obtain this, I used the BITSTRING constructor like this :

...
cam.cam().camParameters().lowFrequencyContainer()().basicVehicleContainerLowFrequency().exteriorLights()=BITSTRING(tmpLights.size * 8 - tmpLights.bits_unused, tmpLights.buf)
...

So I think that the Titan BITSTRING contructor swap a half of the buffer with the other.

Do you think that it's a problem with my code ? Or with the Titan BITSTRING Constructor ?

Best Regards,
Kevin.

[Updated on: Wed, 20 September 2017 04:19] by Moderator

Re: Incorrect bit order Bitstring [message #1772984 is a reply to message #1772971]

Tue, 19 September 2017 13:01

Eclipse User

That is how the TITAN stores the bitstring internally.

The first bit is stored in the LSB of the first octet.

                 Last bit.
'00000100'B
 ^
This is the first bit.

Internally stored in the reversed order, as the bits are filled with from LSB.

You can try:
substr(oct2bit(OCTETSTRING(tmpLights.size,tmpLights.buf)),0,tmpLights.size * 8 - tmpLights.bits_unused)

Re: Incorrect bit order Bitstring [message #1773009 is a reply to message #1772984]

Wed, 20 September 2017 04:17

Eclipse User

Hi Gábor,

It works ! Thanks a lot !

Best Regards,
Kevin.

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