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fivdi / i2c-bus

I2C serial bus access with Node.js
MIT License
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Most significant bit issue using i2cReadSync #3

Closed joraff closed 9 years ago

joraff commented 9 years ago

Seeing a strange issue where the MSB is always set in every byte but the first when using i2cReadSync.

For example, reading the firmware version from a SL030 RFID module results in the buffer: <Buffer 0c f0 80 d3 cc b0 b3 b0 ad b4 ae b0>

Bytes 1 and 2 are correct. Byte 3 should be 00. Bytes 4-12 represent an ASCII string of the firmware version, and the value is correct IF the MSB is removed. The expected buffer is: <Buffer 0c f0 00 53 4c 30 33 30 2D 34 2e 30>

Another example: reading the tag information gives a Buffer of <Buffer 07 81 80 fd d6 f5 ec 81> Here, byte 1 is correct (the length). Bytes 2 and 3 should be 01 and 00. Byte 4 and 5 are correct because the true values should have the MSB set. The rest of the bits mistakenly have their MSB set.

I'm gonna try to dig into the C++, but no promises.... :)

joraff commented 9 years ago

Sorry, should have googled a little more. The SL030 turns out to be a bit of a jerk on the bus. Bumping my baud rate worked.