9 years, 11 months ago.

baud rate problem on Nucleo-F070RB platform

Hi,

I recently purchased a Nucleo-F070RB (MB1136 C-03) from DigiKey, and I have encountered a problem when running the Nucleo_printf example. The code and library documentation say that the default baud rate is 9600, but when I run the code the baud rate is actually 57600. It appears that the PLL is being initialized after the UART, so the UART code initializes BRR as if the system clock will be running at 8 MHz. The system clock is later bumped up to 48 MHz, so the baud rate is off by a factor of 6x.

Here's a gdb session that shows SetSysClock_PLL_HSE() being called after UART_SetConfig(). Note the order in which the breakpoints are encountered.

galens@lion:Nucleo_printf$ /opt/arm/gcc-arm-none-eabi-4_9-2015q1/bin/arm-none-eabi-gdb -q Nucleo_printf.elf 
Reading symbols from Nucleo_printf.elf...done.
(gdb) target extended-remote localhost:3333
Remote debugging using localhost:3333
0x080016b4 in SetSysClock_PLL_HSE ()
(gdb) load
Loading section .text, size 0x4f88 lma 0x8000000
Loading section .ARM.exidx, size 0x8 lma 0x8004f88
Loading section .data, size 0x84 lma 0x8004f90
Start address 0x8000830, load size 20500
Transfer rate: 20 KB/sec, 5125 bytes/write.
(gdb) b SetSysClock_PLL_HSE
Breakpoint 1 at 0x80016b4
(gdb) b UART_SetConfig
Breakpoint 2 at 0x800136a
(gdb) c
Continuing.
Note: automatically using hardware breakpoints for read-only addresses.

Breakpoint 2, 0x0800136a in UART_SetConfig ()
(gdb) backtrace
#0  0x0800136a in UART_SetConfig ()
#1  0x0800157e in HAL_UART_Init ()
#2  0x080017b0 in init_uart ()
#3  0x08001866 in serial_init ()
#4  0x08001c04 in mbed::SerialBase::SerialBase(PinName, PinName) ()
#5  0x08001b86 in mbed::Serial::Serial(PinName, PinName, char const*) ()
#6  0x08000284 in __static_initialization_and_destruction_0 (__initialize_p=1, __priority=65535)
    at main.cpp:8
#7  _GLOBAL__sub_I_pc () at main.cpp:20
#8  0x0800290a in __libc_init_array ()
#9  0x08000862 in LoopFillZerobss ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb) c
Continuing.

Breakpoint 2, 0x0800136a in UART_SetConfig ()
(gdb) backtrace
#0  0x0800136a in UART_SetConfig ()
#1  0x0800157e in HAL_UART_Init ()
#2  0x080017b0 in init_uart ()
#3  0x08001866 in serial_init ()
#4  0x08001c04 in mbed::SerialBase::SerialBase(PinName, PinName) ()
#5  0x08001b86 in mbed::Serial::Serial(PinName, PinName, char const*) ()
#6  0x08000284 in __static_initialization_and_destruction_0 (__initialize_p=1, __priority=65535)
    at main.cpp:8
#7  _GLOBAL__sub_I_pc () at main.cpp:20
#8  0x0800290a in __libc_init_array ()
#9  0x0800016a in _start ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb) c
Continuing.

Breakpoint 1, 0x080016b4 in SetSysClock_PLL_HSE ()
(gdb) backtrace
#0  0x080016b4 in SetSysClock_PLL_HSE ()
#1  0x08001758 in SetSysClock ()
#2  0x080004bc in mbed_sdk_init ()
#3  0x080007ca in __wrap_main ()
#4  0x08000172 in _start ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb) 

I encountered the same baud rate problem when using the binary that I built using the mbed web-based IDE. Note that I am using mbed revision 109.

Am I doing something wrong, or is this a bug?

thanks,
galen