DS90UB929-Q1EVM: Backchannel deactivation at startup

CHEVALLOT Mickael

Part Number: DS90UB929-Q1EVM
Other Parts Discussed in Thread: DS90UB926QSEVB, ALP

I'm using DS90UB929-Q1EVM and DS90UB926QSEVB for converting HDMI to serial and serial to RGB24 data correspondingly,

Between serializer and deserializer, I'm using a unidirectional optical link to transmit the data, so the backchannel communication doesn' work.

The system works well but I have to use Analog LaunchPad software to manually deactivate the backchannel on DS90UB929 device (by setting FORCE_LINK_RDY bit).

Is it possible to deactivate the backchannel of the DS90UB929 device at startup, without using ALP software (I have an embedded microcontroler that can send specific order to the device using I2C or SPI bus) ?

Per advance thank you

Best regards

over 2 years ago

0 Michael.Walker over 2 years ago

TI__Mastermind 19720 points

Hi,

To deactivate the backchannel of the 926 you need to set register 0x01 bit 2: BC Enable to 0.

Regards,

Michael W.

0 CHEVALLOT Mickael over 2 years ago in reply to Michael.Walker

Prodigy 100 points

Hello Michael,

Thanks for your answer.

But my request was focused on the DS929UB929-Q1EVM board. Is there a possibility to deactivate the backchannel at startup of the board ?

Per advance thank you

Best regards

Mickael Chevallot

0 Casey McCrea over 2 years ago in reply to CHEVALLOT Mickael

TI__Guru** 100955 points

Hello Mickael,

The 929 does not provide back channel output. The back channel comes from the deserializer, in this case 926

Best Regards,

Casey

0 CHEVALLOT Mickael over 2 years ago in reply to Casey McCrea

Prodigy 100 points

Hello Casey,

I know that but the 929 device needs the backchannel information to go on sending video information, except if, using the Analog LaunchPad software, we set the bit FORCE_LINK_RDY (register 0x5c of the 929 device).

It works well, but, today, we must use the Analog LaunchPad software to set the bit FORCE_LINK_RDY.

My question was : Can we change the default register value of the DS90UB929-Q1EVM at startup ?

If we can set the FORCE_LINK_RDY bit of the 929 device at startup, I will not need to use Analog LaunchPad software at each startup of the DS90UB929-Q1EVM board.

Best regards

Mickael CHEVALLOT

0 Casey McCrea over 2 years ago in reply to CHEVALLOT Mickael

TI__Guru** 100955 points

Hello Michael,

There is no function to automatically change the default registers for this device. It can only be done after power up using I2C

Best Regards,

Casey

0 CHEVALLOT Mickael over 2 years ago in reply to Casey McCrea

Prodigy 100 points

Hello Casey,

Thanks for your reply.

As I2C bus is monitored by the MSP430 microcontroler of the DS90UB929-Q1EVM board, the only way to change this setting is using the Analog LaunchPad software, isn't it ?

Per advance thank you

Best regards

Mickael CHEVALLOT

0 Casey McCrea over 2 years ago in reply to CHEVALLOT Mickael

TI__Guru** 100955 points

Hello Mickael,

The 929 is configured through standard I2C interface. The ALP GUI just acts an an interface between USB to I2C to issue commands to the I2C interface on 929 so you could use any MCU or processor I2C interface in a system design to control 929 without using ALP

Best Regards,

Casey

0 CHEVALLOT Mickael over 2 years ago in reply to Casey McCrea

Prodigy 100 points

Hello Casey,

Thanks for your answer.

So you mean that, with a PC or a Raspberry Pi for example, we can directly send order through I2C bus through J20 connector of the DS90UB929-Q1EVM board ?

What about VDD voltage on J20 connector ? 1.8V, 3.3V or 5V ?

Concerning I2C bus, as a PC and the MSP430 embedded microcontroler are both master devices, how DS90UB929-Q1EVM board will manage it ?

Per advance thank you

Best regards

Mickael CHEVALLOT

0 Casey McCrea over 2 years ago in reply to CHEVALLOT Mickael

TI__Guru** 100955 points

Hello Mickael,

On the 929 EVM the I2C bus is configurable by jumper setting to 3.3V or 1.8V. See the schematics in the EVM user's guide for details: https://www.ti.com/lit/ug/snlu172/snlu172.pdf?ts=1634837488101&ref_url=https%253A%252F%252Fwww.google.com%252F

The default setting is 3.3V and yes you could connect with a device such as Raspberry Pi to control the 929 using the jumpers on the EVM. If the USB interface is not active to the EVM, then the MSP430 will not be active on the bus trying to send any commands so you can put another master on the bus.

Best Regards,

Casey

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DS90UB929-Q1EVM: Backchannel deactivation at startup