STM8S103F3 PB5/SDA behaves incorrect when used as GPIO

[e_zhui2]

Posted on May 03, 2010 at 11:25

STM8S103F3 PB5/SDA behaves incorrect when used as GPIO

[mozra272]

Posted on May 17, 2011 at 15:08

Hi Dennis,

The I2C pins are configured as true open-drain I/O internally, (P-buffer and protection diode to VDD are not implemented) so is not possible to use them as output pins can you please check with external pull-up 4.7k on these I/O. Regards mozra

[e_zhui2]

Posted on May 17, 2011 at 15:08

Thanks, Mozra.

I am not using the I2C pin to drive 74AC164M now, but with other normal GPIOs. Everything is all right. But I am still using the I2C pins(GPIO mode) to drive other components, currently they work ok. Concerning to your reply ''The I2C pins are configured as true open-drain I/O internally, (P-buffer and protection diode to VDD are not implemented)

so is not possible to use them as output pins

'', I don't know if I am right, is there any underlying risk to use I2C pins as output? Thanks and Regards

[jeffrey23]

Posted on May 17, 2011 at 15:08 Hi Dennis, May I use STM8S103F3 PD5/PD6 as I2C SCL/SDA pins (bit-banging approach) ? Does it mean that I need to switch their configuration according to I2C Read/Write modes ?

    // Setup Port D

    /*     [2]101            7 6 5 4 3 2 1 0            | | | | | | | |            | | |___________ SCL (Output)     Push pull output            | |_____________ SDA (I/O   )     Push pull output     DDR    0 1 1 0 0 0 0 0     CR1    0 1 1 0 0 0 0 0     CR2    0 0 0 0 0 0 0 0     */     GPIOD->DDR = 0x70;     GPIOD->CR1 = 0x70;     GPIOD->CR2 = 0x00;

 Does the STM8S103F3 support 8051 MCU quasi-bidirection mode ?

[jeffrey23]

Posted on May 17, 2011 at 15:08

Dennis,

Do you mean that STM8S103F3 PB.4/PB.5 can be used as normal Open Drain pins ? Could you tell me how to configure their regisers ?     // Init Port B     /*     [2]101            7 6 5 4 3 2 1 0            | | | | | | | |            | | | |_________ I2C SCL (Output)    Open drain output            | | |___________ I2C SDA (Output)    Open drain output     DDR    0 0 1 1 0 0 0 0     CR1    0 0 0 0 0 0 0 0     CR2    0 0 0 0 0 0 0 0     */     GPIOB->DDR = 0x30;     GPIOB->CR1 = 0x00;     GPIOB->CR2 = 0x00; Are they  correct ? What did I miss else ?