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| author | Andrew Dyer <adyer@righthandtech.com> | 2008-12-29 17:36:01 -0600 |
|---|---|---|
| committer | Wolfgang Denk <wd@denx.de> | 2009-01-27 22:26:31 +0100 |
| commit | 2ac6985a7466a1c8a7aa8b2fa24d360925a82764 (patch) | |
| tree | 81c39426e12780c0c88d7634244203916f9f98cf | |
| parent | 3429071700963ca2f944c51d695a7481af0cee33 (diff) | |
| download | u-boot-imx-2ac6985a7466a1c8a7aa8b2fa24d360925a82764.zip u-boot-imx-2ac6985a7466a1c8a7aa8b2fa24d360925a82764.tar.gz u-boot-imx-2ac6985a7466a1c8a7aa8b2fa24d360925a82764.tar.bz2 | |
soft_i2c.c add option for repeated start in i2c_read()
This patch adds a #define to optionally change the behaviour of
i2c_read() in soft_i2c.c to send an I2C repeated start instead of a
stop-start between sending the device address pointer write and
reading back the data. The current behaviour is retained as the
default.
While most devices will work either way, I have a smart battery(*)
that requires repeated start, and someone at some point found a
device that required a stop-start.
(*) http://www.inspired-energy.com/Standard_Products/NL2054/NL2054%20Rev1.0%20Data%20Sheet.pdf
Signed-off-by: Andrew Dyer <adyer@righthandtech.com>
| -rw-r--r-- | README | 9 | ||||
| -rw-r--r-- | drivers/i2c/soft_i2c.c | 12 |
2 files changed, 20 insertions, 1 deletions
@@ -1509,6 +1509,15 @@ The following options need to be configured: Bus on the MPC8260. But it should be not so difficult to add this option to other architectures. + CONFIG_SOFT_I2C_READ_REPEATED_START + + defining this will force the i2c_read() function in + the soft_i2c driver to perform an I2C repeated start + between writing the address pointer and reading the + data. If this define is omitted the default behaviour + of doing a stop-start sequence will be used. Most I2C + devices can use either method, but some require one or + the other. - SPI Support: CONFIG_SPI diff --git a/drivers/i2c/soft_i2c.c b/drivers/i2c/soft_i2c.c index a27de5a..da6cec1 100644 --- a/drivers/i2c/soft_i2c.c +++ b/drivers/i2c/soft_i2c.c @@ -385,8 +385,18 @@ int i2c_read(uchar chip, uint addr, int alen, uchar *buffer, int len) } shift -= 8; } - send_stop(); /* reportedly some chips need a full stop */ + + /* Some I2C chips need a stop/start sequence here, + * other chips don't work with a full stop and need + * only a start. Default behaviour is to send the + * stop/start sequence. + */ +#ifdef CONFIG_SOFT_I2C_READ_REPEATED_START send_start(); +#else + send_stop(); + send_start(); +#endif } /* * Send the chip address again, this time for a read cycle. |