PGA450Q1EVM: Setting up UART communication with ATxmega128A1U micro controller

Alex Bogachenko

Part Number: PGA450Q1EVM
Other Parts Discussed in Thread: PGA460

Hello

I am trying to establish UART communication with the PGA450Q1EVM and our micro controller.
Each device is powered independently. The micro controller is connected to the EVM via the Tx, Rx & GND pins of the RS-232 connector.

The input to the EVM is 5V and the UART settings are baud rate is 19200, 8 bit ,parity disabled and a stop bit is zero.

The message being sent is command0 [0x00, 0x55, 0x01, 0x00]

Using a scope I can see the data get to the EVM but if probing near the PGA itself as appose to near the 232 connector the signal is lowered to 1V so the PGA does not respond.

But sometimes after power cycling the EVM and probing near the PGA I can see the signal that I am sending only inverted in which case the PGA responds with:
[0x00, 0x55, 0x55, 0x00, 0x00, 0x00, 0x7F, 0x00, 0x00,0xF7, 0xF7]

What can be done to correct this?

Thank you
Alex

over 3 years ago

0 Mekre Mesganaw over 3 years ago

TI__Expert 7485 points

Hi Alex,

Can you try the recommendations in the below post:

https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/744251/pga450q1evm-rs232-communication-interface

Also, in general, I recommend the PGA460 for applications instead of the PGA450. The PGA460 has a smaller package, lower cost, improved performance, and ease of programmability and production.

Regards,

Mekre

0 Alex Bogachenko over 3 years ago in reply to Mekre Mesganaw

Prodigy 30 points

Hi Merke

I followed the recommendations in the suggested post and it solved the issue I was having with the PGA not responding, I turned the 5V/3V in the GUI to enable the RS232 circuit.

Unfortunately when I try sending [0x00, 0x55, 0x01, 0x00] via the UART connection the response is [0x00, 0x55, 0x7F]

If I load a custom firmware that only responds with [0x12,0x34] and the checksum in the serial_ISR function the response is still [0x00, 0x55, 0x7F]

Can you please advice on what can be causing this?

Thanks,
Alex

0 Mekre Mesganaw over 3 years ago in reply to Alex Bogachenko

TI__Expert 7485 points

Hi Alex,

Can you try the below:

https://e2e.ti.com/support/data-converters-group/data-converters/f/data-converters-forum/614232/the-question-of-communication-of-uart-on-pga-450

Also, did you try to follow the procedure in Section 4.1.2 of the below document:

https://www.ti.com/lit/an/slda052/slda052.pdf

Regards,

Mekre

0 Alex Bogachenko over 3 years ago

Prodigy 30 points

Hi Merke

I made sure the Tx and Rx are not shorted and after following section 4.1.2 of the relevant document the only response I get is Empty as shown in figure 15 of that document.

Is there anything else you can suggest?

Thanks,
Alex

0 Mekre Mesganaw over 3 years ago in reply to Alex Bogachenko

TI__Expert 7485 points

Hi Alex,

I will do some more digging on this. I should provide my next response by Wednesday.

Regards,

Mekre

0 Alex Bogachenko over 3 years ago in reply to Mekre Mesganaw

Prodigy 30 points

Hi Mekre

Currently the EVM is setup as shown in the picture:

12V supplied to the screw down connector
5V supplied from a different source to 5V test point next to the VPWR-IN
RS232 connected to the computer
Our ATxmega128A1U microcontroller is connected to the EVM via the leads on the left directly to the RxD, TxD and GND of the EVM

I managed to get a response via the USB to UART connection to the RS232 connector what allowed this is to set the Microcontroller State in the GUI to ON (MicroActive) but unfortunately I can not get a response via out microcontroller or via GUI & TI-GER board.

Thanks,
Alex

+1 Mekre Mesganaw over 3 years ago in reply to Alex Bogachenko

TI__Expert 7485 points

Hi Alex,

Thank you for the picture. This cleared a few things up for me. Just to confirm, are you trying to connect the UART pins through the "Communication PCB" header on the left? Can you try connecting to the RXD and TXD test points instead?

Thank you,

Mekre

0 Alex Bogachenko over 3 years ago in reply to Mekre Mesganaw

Prodigy 30 points

Thank you Mekre, after connecting to the RXD and TXD test points communication started working perfectly.
But why is the difference? According to the schematics the communication PCB header pins are connected directly to the test pins.

Thanks,
Alex

0 Mekre Mesganaw over 3 years ago in reply to Alex Bogachenko

TI__Expert 7485 points

Hi Alex,

You were not actually connected to the TXD and RXD pins of the device. The wires you had on the connector are actually connected to a LIN transceiver:

Regards,

Mekre

Sensors

Sensors forum

PGA450Q1EVM: Setting up UART communication with ATxmega128A1U micro controller