ST Micro documentation informs us that UART ports A0 and A1 are surfaced on CN9 pin 1 andCN9 pin3 respectively. Instead I find them on CN11 pin 28 and CN11 pin30. The board is in it's default configuration (no jumpers moved). Is this correct?

[JBend.3]

..

[waclawek.jan]

Which UART? Which board?

JW

[JBend.3]

Oops! I missed that paragraph when pasting my question. Sorry.

I have the NUCLEO-L4A6ZG board and I am configuring UART4 which should provide UART4-TX on PA0 (CN9 pin 1) and UART4-RX on PA1 (CN9 pin3).

I have just discovered that according to the STM32 Nucleo-144 boards (MB1312) documentation:

UART4 PA0 is not connected to CN9 pin 1 if solder bridge SB179 is made. There appears to be a resistor on this bridge.

I can't see why PA1 is not exposed on CN9 pin 3 though.

[Tesla DeLorean]

https://www.st.com/resource/en/schematic_pack/mb1312-l4xxzx-a03_schematic.pdf

[JBend.3]

Thank you for the board schematic. I have had a good look, but I don't see an answer to my question.

[Tesla DeLorean]

Which one?

>>I can't see why PA1 is not exposed on CN9 pin 3 though.

Because CN9.3 is shown to connect too PC1, the "A1" is an Arduino pin designation for Analogue#1, not STM32 PA1

CN9.1 PA3 "A0"

[JBend.3]

Thank you. I understand what the schema and documentation is presenting.

The NUCLEO board documentation is assuming the reader has knowledge of the Arduino. A few well chosen words on the documentation would have saved hours of pain. I am new to St Micro having worked with Microchip and Atmel devices for years. I will be more careful in the future.

[Tesla DeLorean]

Arduino has used the A# and D# pin designations on the shields/boards for 15+ years,

Atmel/Microchip has by far the biggest number of design wins for Arduino products.

The Nucleo boards were built to use/extend the Arduino Uno R3 type shield connector, with more expansive pin escape.

The schematic nets clearly identify the pin naming on the STM32 side. Some of the solder bridging and routing options I would agree add a level of complexity, but it is generally there to a) accommodate multiple IC usage for the board, and b) provide enough wiggle room to address corner cases of occasional Arduino usage vs pin/peripheral mapping limitations. ie getting I2C pins to come out of some analogue pins.

The manual tables for the Nucleo identify the designations, and the graphical pictures of the headers show the STM32 pin associativity.

I think this is an issue of you seeing past the object in front of you, woods vs trees, and not a lack of documentation.

[JBend.3]

Thank you Tesla DeLorean.

Actually, I think it is an issue of me having never worked with Arduino (as I said) and the NUCLEO pin-out documentation not being quite as clear as St Micro perhaps intended.

Thank you for your help.