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Fixing bug in Wire library that caused it to read and discard one extra byte when do a requestFrom() a slave device. Thanks to Christopher K. Johnson.

This commit is contained in:
David A. Mellis 2009-06-20 20:43:24 +00:00
parent 15cff82214
commit 6ba23bafe2

View File

@ -135,7 +135,12 @@ uint8_t twi_readFrom(uint8_t address, uint8_t* data, uint8_t length)
// initialize buffer iteration vars
twi_masterBufferIndex = 0;
twi_masterBufferLength = length;
twi_masterBufferLength = length-1; // This is not intuitive, read on...
// On receive, the previously configured ACK/NACK setting is transmitted in
// response to the received byte before the interrupt is signalled.
// Therefor we must actually set NACK when the _next_ to last byte is
// received, causing that NACK to be sent in response to receiving the last
// expected byte of data.
// build sla+w, slave device address + w bit
twi_slarw = TW_READ;