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| author | David A. Mellis <d.mellis@arduino.cc> | 2009-06-20 20:43:24 +0000 |
|---|---|---|
| committer | David A. Mellis <d.mellis@arduino.cc> | 2009-06-20 20:43:24 +0000 |
| commit | 6b62b244d51d93f670c6f9e80ba92da3aceff947 (patch) | |
| tree | 0326f05a8e7803cc9678886abdda835d4d406867 /libraries/Wire/utility/twi.c | |
| parent | c3baee9f63f7876bb30d128ee6e59cc0266312a9 (diff) | |
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.
Diffstat (limited to 'libraries/Wire/utility/twi.c')
| -rw-r--r-- | libraries/Wire/utility/twi.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/libraries/Wire/utility/twi.c b/libraries/Wire/utility/twi.c index 82a25c0..bfa917a 100644 --- a/libraries/Wire/utility/twi.c +++ b/libraries/Wire/utility/twi.c @@ -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; |