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@@ -39,11 +39,14 @@
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static TU_ATTR_ALIGNED(4) UsbDeviceDescBank sram_registers[8][2];
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// Setup packet is only 8 bytes in length. However under certain scenario,
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-// SAMD21 USB DMA controller is "suspected" to overwrite/overflow the setup_packet with 2 extra bytes.
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-// Which corrupt other variable and cause issue such as
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-// https://github.com/adafruit/circuitpython/issues/3912 (on macOS)
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-// Therefore we increase it to 12 bytes as walk-around until figuring out the root cause
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-static TU_ATTR_ALIGNED(4) uint8_t _setup_packet[8+4];
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+// USB DMA controller may decide to overwrite/overflow the buffer with
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+// 2 extra bytes of CRC. From datasheet's "Management of SETUP Transactions" section
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+// If the number of received data bytes is the maximum data payload specified by
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+// PCKSIZE.SIZE minus one, only the first CRC data is written to the data buffer.
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+// If the number of received data is equal or less than the data payload specified
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+// by PCKSIZE.SIZE minus two, both CRC data bytes are written to the data buffer.
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+// Therefore we will increase it to 10 bytes just to be safe
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+static TU_ATTR_ALIGNED(4) uint8_t _setup_packet[8+2];
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// ready for receiving SETUP packet
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static inline void prepare_setup(void)
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hathach