[BUG]: Broken Implementation of WPILib SPI about robotpy-wpilib HOT 7 CLOSED

Also, my understanding is that many SPI devices require you to write something in order to read it, which is why an API like transaction exists. So maybe you're just not telling the device to send any data, so it isn't.

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bytes are readonly in python. I believe if you use a bytearray instead then it will work.

It should give a good error message when you pass in a bytes... what error message do you get when you do that? We can try to make the error better in the future.

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I will try that today. I get no type error when invoking the function (but I do when trying to pass something like [] instead of bytes), it just gives me a segmentation fault with a traceback to the read function. Is there any way I can specify the size of the read? Will it just be the size of my bytearray?

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Yes, it should be the size of your bytearray.

I'll see if I can take a look tonight.

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The function returns the size of my bytearray, so I think you're right. However, when I try to initiate a read the bytearray is unmodified and the function doesn't error even when no SPI device is connected. Is this intended behavior?

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The binding looks right to me. Here's what robotpy-build autogenerates to bind the function:

.def("read", [](frc::SPI * __that,bool initiate, const py::buffer& dataReceived) {
          int size = 0;
          auto __dataReceived = dataReceived.request(true);
          size = __dataReceived.size * __dataReceived.itemsize;
          auto __ret =__that->Read(initiate, (uint8_t*)__dataReceived.ptr, size );
          return __ret;
        },

Looking at SPI::Read it looks like the return value should be ... something undocumented. According to HAL, it looks like the return value should be whatever ioctl is going to return: ... which is likely going to be the length of data written?

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I'm going to close this as I don't believe there's a bug here, just the error message needs improvement.

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