diff options
Diffstat (limited to 'README')
| -rw-r--r-- | README | 63 |
1 files changed, 51 insertions, 12 deletions
@@ -653,6 +653,9 @@ The following options need to be configured: CONFIG_RTC_DS1338 - use Maxim, Inc. DS1338 RTC CONFIG_RTC_DS164x - use Dallas DS164x RTC + Note that if the RTC uses I2C, then the I2C interface + must also be configured. See I2C Support, below. + - Timestamp Support: When CONFIG_TIMESTAMP is selected, the timestamp @@ -904,29 +907,48 @@ The following options need to be configured: - I2C Support: CONFIG_HARD_I2C | CONFIG_SOFT_I2C - Enables I2C serial bus commands. If this is selected, - either CONFIG_HARD_I2C or CONFIG_SOFT_I2C must be defined - to include the appropriate I2C driver. + These enable I2C serial bus commands. Defining either of + (but not both of) CONFIG_HARD_I2C or CONFIG_SOFT_I2C will + include the appropriate I2C driver for the selected cpu. - See also: common/cmd_i2c.c for a description of the + This will allow you to use i2c commands at the u-boot + command line (as long as you set CFG_CMD_I2C in + CONFIG_COMMANDS) and communicate with i2c based realtime + clock chips. See common/cmd_i2c.c for a description of the command line interface. + CONFIG_HARD_I2C selects the CPM hardware driver for I2C. + + CONFIG_SOFT_I2C configures u-boot to use a software (aka + bit-banging) driver instead of CPM or similar hardware + support for I2C. - CONFIG_HARD_I2C + There are several other quantities that must also be + defined when you define CONFIG_HARD_I2C or CONFIG_SOFT_I2C. - Selects the CPM hardware driver for I2C. + In both cases you will need to define CFG_I2C_SPEED + to be the frequency (in Hz) at which you wish your i2c bus + to run and CFG_I2C_SLAVE to be the address of this node (ie + the cpu's i2c node address). + + Now, the u-boot i2c code for the mpc8xx (cpu/mpc8xx/i2c.c) + sets the cpu up as a master node and so its address should + therefore be cleared to 0 (See, eg, MPC823e User's Manual + p.16-473). So, set CFG_I2C_SLAVE to 0. - CONFIG_SOFT_I2C + That's all that's required for CONFIG_HARD_I2C. - Use software (aka bit-banging) driver instead of CPM - or similar hardware support for I2C. This is configured - via the following defines. + If you use the software i2c interface (CONFIG_SOFT_I2C) + then the following macros need to be defined (examples are + from include/configs/lwmon.h): I2C_INIT - (Optional). Any commands necessary to enable I2C + (Optional). Any commands necessary to enable the I2C controller or configure ports. + eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |= PB_SCL) + I2C_PORT (Only for MPC8260 CPU). The I/O port to use (the code @@ -939,32 +961,49 @@ The following options need to be configured: (driven). If the data line is open collector, this define can be null. + eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |= PB_SDA) + I2C_TRISTATE The code necessary to make the I2C data line tri-stated (inactive). If the data line is open collector, this define can be null. + eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA) + I2C_READ Code that returns TRUE if the I2C data line is high, FALSE if it is low. + eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0) + I2C_SDA(bit) If <bit> is TRUE, sets the I2C data line high. If it is FALSE, it clears it (low). + eg: #define I2C_SDA(bit) \ + if(bit) immr->im_cpm.cp_pbdat |= PB_SDA; \ + else immr->im_cpm.cp_pbdat &= ~PB_SDA + I2C_SCL(bit) If <bit> is TRUE, sets the I2C clock line high. If it is FALSE, it clears it (low). + eg: #define I2C_SCL(bit) \ + if(bit) immr->im_cpm.cp_pbdat |= PB_SCL; \ + else immr->im_cpm.cp_pbdat &= ~PB_SCL + I2C_DELAY This delay is invoked four times per clock cycle so this controls the rate of data transfer. The data rate thus - is 1 / (I2C_DELAY * 4). + is 1 / (I2C_DELAY * 4). Often defined to be something + like: + + #define I2C_DELAY udelay(2) CFG_I2C_INIT_BOARD |
