SN65HVD72: Production Testing

Dharmesh Joshi

Part Number: SN65HVD72
Other Parts Discussed in Thread: THVD1406

Tool/software:

Hi,

We are going to be using the SN65HVD72 on an upcoming PCB as an interface for future communication with additional PCBs. At the moment, we do not have any PCBs to communicate with. Is there any way we can perform a test to ensure that the IC is working with our UART port and is ready for communication in the future?

In addition to this, would I be correct in understanding that, as this is a half-duplex device, I would need to toggle the IC when my microcontroller transmits and receives messages? Or can it be set up so that I do not need to toggle any GPIO and just focus on the UART data?

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 316640 points

With one PCB alone, the best you can do is loopback testing.

You indeed need to toggle the DE pin to ensure that at most one node is active. The only way to avoid this would be the THVD1406.

0 Dharmesh Joshi over 1 year ago in reply to Clemens Ladisch

Expert 1895 points

Clemens Ladisch Thank You for your reply.

How do we configure a loop-back test?

So, if I understand correctly, only the device that is when a device TX a message should have DE high; otherwise, it needs to be low, but RE for all devices can always be set to low.

0 Clemens Ladisch over 1 year ago in reply to Dharmesh Joshi

Guru 316640 points

On a half-duplex transceiver, the receiver is already connected to the driver, so you do not have to configure anything.

Yes, DE must be switched, and /RE can always be low. (Sometimes, DE and /RE are controlled with the same signal to avoid receiving what you are sending. But this is not what you want for loop-back testing.)

0 BOBBY over 1 year ago

TI__Guru 72521 points

Hi Dharmesh,

We do have an evaluation module for our half duplex single channel RS485 devices like SN65HVD72: https://www.ti.com/tool/RS485-HF-DPLX-EVM

You can use this to evaluate the UART communication through a cable.

Yes you would need to toggle the DE/RE pins to switch between transmitting and receiving unless you decide to use a full duplex RS485 transceiver.

-Bobby

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SN65HVD72: Production Testing