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qi-fix-i2c-multiread-nack-nak.patch

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On the last read, master must NAK, on intermediate reads it must ACK.
If you get this wrong, communication with device is screwed even in Linux.

Signed-off-by: Andy Green <andy@openmoko.com>
This commit is contained in:
Andy Green 2008-11-28 10:16:39 +00:00 committed by Andy Green
parent 64f0faee54
commit e55b148f55
1 changed files with 23 additions and 6 deletions
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27
qiboot/src/drivers/i2c-bitbang.c
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@ -53,14 +53,17 @@ int i2c_next_state(struct i2c_bitbang * bb)
case IBS_INIT:
bb->index = 0;
bb->index_read = 0;
/* fall thru */
(bb->set)(1, 1);
bb->state = IBS_START1;
break;
case IBS_START1:
(bb->set)(1, 0);
(bb->set)(0, 0); /* start */
bb->state = IBS_START2;
break;
case IBS_START2:
(bb->set)(0, 0); /* start */
bb->count = 8;
bb->state = IBS_ADS_TX_S;
break;
@ -137,25 +140,34 @@ int i2c_next_state(struct i2c_bitbang * bb)
case IBS_DATA_RX_L:
bb->data[bb->index_read] <<= 1;
bb->data[bb->index_read] |= !!(bb->read_sda)();
(bb->set)(0, 1);
bb->count--;
if (bb->count) {
(bb->set)(0, 1);
bb->state = IBS_DATA_RX_S;
break;
}
/* slave has released SDA now, bang down ACK */
if (bb->data[bb->index + 1] != IBCONTROL_DO_READ)
(bb->set)(0, 1);
else
(bb->set)(0, 0);
bb->state = IBS_DATA_RX_ACK_H;
break;
case IBS_DATA_RX_ACK_H:
(bb->set)(1, 0);
if (bb->data[bb->index + 1] != IBCONTROL_DO_READ)
(bb->set)(1, 1); /* NAK */
else
(bb->set)(1, 0); /* ACK */
bb->state = IBS_DATA_RX_ACK_L;
break;
case IBS_DATA_RX_ACK_L:
(bb->set)(0, 1);
if (bb->data[bb->index + 1] != IBCONTROL_DO_READ)
(bb->set)(0, 1); /* NAK */
else
(bb->set)(0, 0); /* ACK */
bb->index_read++;
bb->index++;
switch (bb->data[bb->index]) {
@ -214,6 +226,11 @@ static int i2c_complete_synchronously(struct i2c_bitbang * bb)
(bb->spin)();
}
if (ret < 0) {
puts("i2c transaction failed ");
printdec(ret);
puts("\n");
}
return ret;
}