stm32l4r5zit6 VS stm32l4r5zit6p Uart conflict

[Adrián Cobos]

Hello good Morning,

We have tried to make some cards, but our manufacturer has made a mistake and has mounted the stm32l4r5zit6p instead of stm32l4r5zit6.

It seems that we are able to correctly program the uC through the REALICE tool (using st-link for connect, erase, read, program internal memory), but the uC has strange behaviors, for example:

The uart3, which we have configured on pins PC_12 and PD_2, does not work correctly.

We have tried a very simple program code (shown below) using an old board with the stm32l4r5zit6, and also with new one, stm32l4r5zit6p.

 #include "mbed.h"
#define 	MAX_LOG_SIZE 	2048
 
UnbufferedSerial 	USB 		(PC_12, PD_2, 115200); //TX, RX
	char buf_log[MAX_LOG_SIZE] = {0};
    uint32_t num_log;
 
int main(void){
	while (1)
	{
 
	ThisThread::sleep_for(2s);
 
	num_log = sprintf(buf_log, "\n\r--- START TEST PROGRAM\n\r");
        USB.write(buf_log, num_log);  
	}
}

When we power the old one, it send information through the uart pins, putting the RX and TX signal at high level (we check with osciloscope), so the old board works perfectly. But the new one doesn´t send anything and RX and TX pins get low level forever.

Reading datasheet we have notice that there is some differences at pinouts and functionality between both board. But differences that we notice are no related with this uart so we cant comfirm if differences that we check are affectting this point.

[TDK]

Are PB11 and PE1 used on your board? The "P" suffix version needs these pins free to supply ~1.2V on them.

What happens when you debug the program and step through the code?

[Adrián Cobos]

Hello TDK, thank for answering!

First of all, In order to clarify: we dont want to use power functions of model P, we only want to know if model P and "not P" are equivalent.

PB11 is unused in our circuit, but PE1 is used as a digital output in order to control a Bluetooth module.

If we run and debug our main program (or the test code above), uC appers to run correctly and try to send information through the uart; however, if we put oscilloscope at RX and TX lines, these lines are low state or desactivated.

[TDK · Accepted solution]

> Reading datasheet we have notice that there is some differences at pinouts and functionality between both board.

> we only want to know if model P and "not P" are equivalent.

No, they're not equivalent. The pinout is (slightly) different. In particular, PE1 (pin 142) on the STM32L4R5ZIT6 is VDD12 on the STM32L4R5ZIT6P. If you're driving this pin to 3.3V externally, the chip behavior is undefined.