Andreas Bießmann schrieb:
Am 01.06.2010 16:04, schrieb Reinhard Meyer (-VC):
Hi,
Dear Reinhard Meyer,
has anyone started or completed work on an I2C driver for AP7000x?
No ...
If not, I am at least going to make SOFT I2C defines to read VPD from an At24C64 EEPROM.
But I've working soft-i2c here. There are still some other examples in u-boot how to interface a at24xx eeprom.
Thank you. That worked to verify my setup. I was fooled by the AtTiny on the NGW100 which does try to slow I2C Transfers by pulling SCL low. That feature however is NOT honored by the SOFT_I2C driver. So accesses to my At24C64 had to fail. After removing the AtTiny it works fine :)
custom board config file: ---8<--- /* i2c definitions */ #define CONFIG_SOFT_I2C #if defined(CONFIG_SOFT_I2C) #define DEBUG_I2C #ifndef __ASSEMBLY__ #include <asm/arch/portmux.h> #define MEDUCORE_SDA_PIN 6 #define MEDUCORE_SCL_PIN 7
#define I2C_ACTIVE portmux_select_gpio(PORTMUX_PORT_A, (1<<MEDUCORE_SDA_PIN), PORTMUX_DIR_OUTPUT|PORTMUX_INIT_LOW) #define I2C_TRISTATE portmux_select_gpio(PORTMUX_PORT_A, (1<<MEDUCORE_SDA_PIN), PORTMUX_DIR_INPUT|PORTMUX_OPEN_DRAIN)
The functions ACTIVE and TRISTATE are not required when the Pins are initialized OUTPUT and OPENDRAIN as follows:
int board_early_init_f(void) { ... #ifdef CONFIG_CMD_I2C // first select SCL and SDA gpio portmux_select_gpio(PORTMUX_PORT_A,(1<<SDA_PIN), PORTMUX_DIR_OUTPUT|PORTMUX_INIT_LOW|PORTMUX_OPEN_DRAIN); portmux_select_gpio(PORTMUX_PORT_A,(1<<SCL_PIN), PORTMUX_DIR_OUTPUT|PORTMUX_INIT_LOW|PORTMUX_OPEN_DRAIN); // initialize i2c i2c_init(1000, 0x27); #endif return 0; }
The I2C Bus by definition is a wired-or bus, all devices must have open drain outputs for SDA and SCL!
Best Regards, Reinhard