Need some help setting up UART5

[gradoj]

I am trying to get UART 5 up and running on a custom board. I've made a couple of modifications but when I .read it always returns with no data and when I .write nothing goes out on uart 5.

If anyone can point out where I've gone wrong I'd appreciate it. Is there a way to query the pins to see if they are setup for their alternate function?

mpconfigboard.h

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#define MICROPY_HW_UART5_PORT (GPIOC)
#define MICROPY_HW_UART5_PINS (GPIO_PIN_12)

uart.c in uart_init2 I tried with the commented lines in and out

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#if defined(UART5) && defined(MICROPY_HW_UART5_PORT) && defined(MICROPY_HW_UART5_PINS)
case PYB_UART_5:
	UARTx = UART5;
        irqn = UART5_IRQn;
        GPIO_AF_UARTx = GPIO_AF8_UART5;
			
        GPIO_Port = MICROPY_HW_UART5_PORT;
        GPIO_Pin = MICROPY_HW_UART5_PINS;
	__UART5_CLK_ENABLE();
			
	GPIO_InitTypeDef GPIO_InitStructure;
	GPIO_InitStructure.Pin = GPIO_PIN_2;
	//GPIO_InitStructure.Speed = GPIO_SPEED_HIGH;
	//GPIO_InitStructure.Mode = GPIO_MODE_AF_PP;
	//GPIO_InitStructure.Pull = GPIO_PULLUP;
	GPIO_InitStructure.Alternate = GPIO_AF_UARTx;
	HAL_GPIO_Init(GPIOD, &GPIO_InitStructure);
break;
#endif

and in uart.c deinit

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#if defined(UART5)
    } else if (uart->Instance == UART5) {
        HAL_NVIC_DisableIRQ(UART5_IRQn);
        __UART5_FORCE_RESET();
        __UART5_RELEASE_RESET();
        __UART5_CLK_DISABLE();
#endif

[gradoj]

It looks like those pins are not getting set to their alternate functions:

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>>> a=pyb.Pin.board.PD2
>>> b=pyb.Pin.board.PC12
>>> a
Pin(Pin.cpu.D2, mode=Pin.IN)
>>> b
Pin(Pin.cpu.C12, mode=Pin.IN)
>>> a.af()
0
>>> b.af()
0
>>> a.af_list()
[Pin.AF2_TIM3, Pin.AF8_UART5]
>>> b.af_list()
[Pin.AF6_SPI3, Pin.AF7_USART3, Pin.AF8_UART5]

[dhylands]

Your code seems to have the line which sets the alternate function commented out. In particular:

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   //GPIO_InitStructure.Mode = GPIO_MODE_AF_PP;

You really should initialize all of the fields, otherwise they get random values off the stack.

[gradoj]

I put the commented out lines back in but the pins still do not get configured for their alternate function. It appears something isn't working in the new code I added to initialize UART5. When I configured the pins manually for their alternate function of uart5 and send bytes to that uart the REPL stops responding. Any strategies on debugging something like this?

[Damien]

A few things to check:

1. You need to define both the RX and TX pins in the MICROPY_HW_UART5_PINS macro.
2. You will need to add a UART5 irq handler in stm32f4xx_it.c.
3. You need to create and instance of the UART to set it up: pyb.UART(5, 9600).

[gradoj]

1. You need to define both the RX and TX pins in the MICROPY_HW_UART5_PINS macro.
2. You will need to add a UART5 irq handler in stm32f4xx_it.c.
3. You need to create and instance of the UART to set it up: pyb.UART(5, 9600).

1. tx and rx pins for uart5 are on different ports PC12 and PD12. I didnt see how I could use the existing macros. That is why I hardcoded the one pin in uart.c init for now. This may be messing something up?
2. I missed the irq handler. Thanks
3. I can send and receive on other uart ports so pretty sure im using it correctly

[Damien]

Note that PD2 is used as the SD card CMD pin, so the SD card will need to be disabled.

Here is what I get for UART(4):

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>>> pyb.UART(4, 9600)
UART(4, baudrate=9600, ...)
>>> pyb.Pin.board.X1
Pin(Pin.cpu.A0, mode=Pin.AF_PP, pull=Pin.PULL_UP, af=Pin.AF8_UART4)
>>> pyb.Pin.board.X2
Pin(Pin.cpu.A1, mode=Pin.AF_PP, pull=Pin.PULL_UP, af=Pin.AF8_UART4)

[gradoj]

I was assuming from the af() that the pins were not in alternative function mode but it looks like they are. What does the af() function tell me?

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>>> import pyb
>>> pyb.UART(5,115200)
UART(5, baudrate=115384, bits=8, parity=None, stop=1, timeout=1000, timeout_char=0, read_buf_len=64)
>>> pyb.Pin.board.PD2
Pin(Pin.cpu.D2, mode=Pin.AF_PP, pull=Pin.PULL_UP, af=Pin.AF8_UART5)
>>> pyb.Pin.board.PC12
Pin(Pin.cpu.C12, mode=Pin.AF_PP, pull=Pin.PULL_UP, af=Pin.AF8_UART5)

I don't see anything come out the uart with the write command. The read returns nothing like it should but as soon as I send a character to UART5 the REPL(which is on UART1) stops responding.

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>>> a=pyb.UART(5,115200)
>>> a.write('asdf')
4
>>> a.read()
b''

[dhylands]

The Pin.af() functions tells you the currently configured alternate function for the pin.

But the af() is only meaningful when Pin.mode() reports one of pyb.Pin.AF_PP or pyb.Pin.AF_OD. For all other modes, what af() reports is irrelevant.

I wrote a little script which you can find in the examples directory called pins.py. If you copy pins.py and the pins_af.py (from the stmhal/build-PYBV10 directory for your board) onto the pyboard and then from the pyboard REPL do this:

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>>> import pins
>>> pins.pins()
X1         IN                          
X2         IN                          
X3         IN                          
X4         IN                          
X5         IN                          
X6         IN                          
X7         IN                          
X8         IN                          
X9         IN                          
X10        IN                          
X11        IN                          
X12        IN                          
X17        IN     PULL_UP              
X18        IN                          
X19        IN                          
X20        IN                          
X21        IN                          
X22        IN                          
Y1         AF_PP  PULL_UP 8: USART6_TX 
Y2         AF_PP  PULL_UP 8: USART6_RX 
Y3         IN                          
Y4         IN                          
Y5         IN                          
Y6         IN                          
Y7         IN                          
Y8         IN                          
Y9         IN                          
Y10        IN                          
Y11        IN                          
Y12        IN                          
SW         IN     PULL_UP              
LED_RED    OUT_PP                      
LED_GREEN  OUT_PP                      
LED_YELLOW OUT_PP                      
LED_BLUE   AF_PP          2: TIM3_CH1  
MMA_INT    IN                          
MMA_AVDD   OUT_PP                      
SD_D0      AF_PP  PULL_UP 12           
SD_D1      AF_PP  PULL_UP 12           
SD_D2      AF_PP  PULL_UP 12           
SD_D3      AF_PP  PULL_UP 12           
SD_CMD     AF_PP  PULL_UP 12           
SD_CK      AF_PP  PULL_UP 12           
SD         IN     PULL_UP              
SD_SW      IN     PULL_UP              
USB_VBUS   IN                          
USB_ID     AF_OD  PULL_UP 10           
USB_DM     AF_PP          10           
USB_DP     AF_PP          10 

Basically it reports the current configuration for each pin.

[gradoj]

Thanks. Pins.py will be a handy little script. I forgot to mention that I have disabled the SD card as one of the UART5 pins overlaps with it so I have no external filesystem for now.

I guess I ran .af() before I initialized the uart before and got fooled into thinking the alternate function wasn't setup properly.

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>>> pc12=pyb.Pin.board.PC12
>>> pc12
Pin(Pin.cpu.C12, mode=Pin.IN)
>>> pc12.af()
0
>>> u5=pyb.UART(5,115200)
>>> u5
UART(5, baudrate=115384, bits=8, parity=None, stop=1, timeout=1000, timeout_char=0, read_buf_len=64)
>>> pc12
Pin(Pin.cpu.C12, mode=Pin.AF_PP, pull=Pin.PULL_UP, af=Pin.AF8_UART5)
>>> pc12.af()
8
>>>

So this is strange. It seems the uart5 is setup correctly but I cannot get anything out of it and if I write anything in to it something seems to crash.