Linux/PROCESSOR-SDK-AM437X: EVM LEDs not working as expected

Phillip Holtzman

Part Number: PROCESSOR-SDK-AM437X
Other Parts Discussed in Thread: TPIC2810

Tool/software: Linux

The AM437x Industrial EVM contains an LED driver at I2C address 0x60 (User's Manual, Table 3). Hardware is TPIC2810, 8-bit LED driver.

I am using subaddress 44H to write data to the data shift register and transfer the data to the output storage register immediately.

The code below seems to work fine, but LEDs D3..D10 are not working as expected. A walking 1's pattern shows that some LEDs are affecting others.

    mSMbusData.read_write = I2C_SMBUS_WRITE;
    mSMbusData.command = 0x44;
    mSMbusData.size = I2C_SMBUS_BYTE_DATA;
    mSMbusData.data = &I2CData;

    I2CData.byte = value;

    ioctl(mFileDescriptor, I2C_SMBUS, &mSMbusData);

Questions:
1. Are all LEDs (D3..D10) under software control?
2. What is the advantage of writing data to the shift register (subaddress 11H) and transferring to the output storage register (subaddress 22H) in 2 separate steps? Why provide that option.
3. What is driving the LEDs other than the TPIC2810? Are they tied to some onboard status that would interfere with software control?

over 6 years ago

0 Biser Gatchev-XID over 6 years ago

TI__Guru**** 393215 points

Which SDK is this? Which version?

0 Phillip Holtzman over 6 years ago in reply to Biser Gatchev-XID

Intellectual 380 points

ti-processor-sdk-linux-am437x-evm-05.02.00.10

0 Nick Saulnier over 6 years ago in reply to Phillip Holtzman

TI__Guru** 101660 points

Hello Phillip,

It looks like you can use the gpio-leds Linux driver to control the LEDs - the first step would be to enable the leds-iio node of the device tree as Kemal discusses in the post i2c led driver. Do you still get unusual behavior when using the LED driver?

Regards,

Nick

0 Phillip Holtzman over 6 years ago in reply to Nick Saulnier

Intellectual 380 points

The problem is not accessing the LEDs, the problem is the LEDs do not work as expected.

Writing to any LED for 3+ seconds triggers a test pattern, 01, 03, 07, 0F, 1F, 3F, 7F, FF, where is MSB is D10 and the LSB is D3.

Can the test pattern be disabled?

0 Nick Saulnier over 6 years ago in reply to Phillip Holtzman

TI__Guru** 101660 points

Hello Phillip,

I enabled the leds-iio node for AM437x IDK as per my previous post, and I verified that all 8 LEDs were under software control and behaving as expected with commands like

echo "1" > /sys/class/leds/out0/brightness
echo "0" > /sys/class/leds/out0/brightness

I do not expect that any other driver is using the LEDs, since no other nodes reference tpic2810 in the am437x-idk-evm.dts device tree.

So from a Linux standpoint, the LEDs are behaving as expected. Let me know if you want us to reassign the thread for someone from the tpic team to comment on your in-depth questions on loading tpic values.

Regards,
Nick

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Linux/PROCESSOR-SDK-AM437X: EVM LEDs not working as expected