[PATCH 7/7] qi-fix-i2c-multiread-nack-nak.patch
Andy Green
andy at openmoko.com
Fri Oct 10 12:51:58 CEST 2008
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 at openmoko.com>
---
src/drivers/i2c-bitbang.c | 29 +++++++++++++++++++++++------
1 files changed, 23 insertions(+), 6 deletions(-)
diff --git a/src/drivers/i2c-bitbang.c b/src/drivers/i2c-bitbang.c
index eef28a6..436003e 100644
--- a/src/drivers/i2c-bitbang.c
+++ b/src/drivers/i2c-bitbang.c
@@ -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 */
- (bb->set)(0, 0);
+ 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;
}
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