TCA9554: Technical issues

switch

Part Number: TCA9554
Other Parts Discussed in Thread: PCF8574, PCA9554

Tool/software:

Hi ti team，

The GPIO expansion was successful, but I failed to operate this node using ADB, such as changing the output. For example, echo out > gpio504/direction still results in in.

10 months ago

0 Tyler Townsend 10 months ago

TI__Mastermind 47328 points

Hi Switch,

What exactly am I looking at in the image provided, and what is the problem?

Is the TCA9554 not being detected by your i2c driver?

Regards,

Tyler

0 Clemens Ladisch 10 months ago

Guru 316690 points

The PCF8574 has quasi-bidirectional I/O pins; their direction cannot be configured.

0 switch 10 months ago in reply to Tyler Townsend

Genius 3750 points

Hi Tyler，

According to the documentation, register 0x03 is configured as 0x00 and GPIO can be configured as output, but the actual i2cset -fy 0 0x20 0x03 0xff b can see that GPIO is still input, GPIO only becomes low, please help to analyze it.

0 liu qin 10 months ago in reply to Clemens Ladisch

Prodigy 40 points

Hi Tyler，

When I use command " echo 0 > gpio504/value", also can't change value from high to low, why?

0 Tyler Townsend 10 months ago in reply to liu qin

TI__Mastermind 47328 points

Hi Liu and Switch,

Just to be clear, we are talking to the TCA9554 device and not the PCF8574 correct?

TCA9554 has configurable registers, PCF8574 does not.

switch said:
According to the documentation, register 0x03 is configured as 0x00 and GPIO can be configured as output, but the actual i2cset -fy 0 0x20 0x03 0xff b can see that GPIO is still input, GPIO only becomes low, please help to analyze it.

Correct me if I am wrong, but the I2Cset command you just mentioned looks to be writing 0xFF data to the register to set it to output? This is incorrect. To configure the pins as OUTPUT's you would need to write 0x00 to the configuration register located at 0x03.

liu qin said:
When I use command " echo 0 > gpio504/value", also can't change value from high to low, why?

Do we have any oscilloscope captures of the commands you are attempting to write to the IO expander?

Regards,

Tyler

0 liu qin 10 months ago in reply to Tyler Townsend

Prodigy 40 points

1、Actually TCA9554 ,but driver use "gpio-pcf857x.c".

2、i2cset -fy 0 0x20 0x03 0x0f b, all gpios still show input, just some gpios change frome high to low

0 Clemens Ladisch 10 months ago in reply to liu qin

Guru 316690 points

The TCA9554 and the PCF8574 are different devices and use different drivers. The TCA9554's compatible ID is "nxp,pca9554".

0 liu qin 10 months ago in reply to Clemens Ladisch

Prodigy 40 points

Please share drivers to me , thanks

0 Tyler Townsend 10 months ago in reply to liu qin

TI__Mastermind 47328 points

Hi Liu,

We do not provide drivers or source code from TI side.

However, I found a github that might have some useful code. It looks to be the driver for PCA9554, but it should be essentially the same as the TCA9554.

linux-tronsmart-orion-r28/drivers/gpio/pca9554.c at master · lgeek/linux-tronsmart-orion-r28 · GitHub

Regards,

Tyler

0 Clemens Ladisch 10 months ago in reply to liu qin

Guru 316690 points

The name of the driver is gpio-pca953x; it is enabled with the kernel configuration symbol CONFIG_GPIO_PCA953X. In the DeviceTree configuration, its compatible ID is "nxp,pca9554".

0 liu qin 10 months ago in reply to Clemens Ladisch

Prodigy 40 points

Thanks , resolved. I have no question anymore.

0 Tyler Townsend 10 months ago in reply to liu qin

TI__Mastermind 47328 points

Hi Liu,

Awesome! If you have any additional questions please feel free to reach out.

Regards,

Tyler

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TCA9554: Technical issues