USART2 on ComStick (STM32F107)

You have a question?

http://www.catb.org/~esr/faqs/smart-questions.html#before

yes.. there was... but somehow i deleted. i explain it again:

i would like to use usart2 on this device; in particular i choosed the configuration on PORTD remapped from pins 3 to 7. Here's my code:

 GPIO_InitTypeDef GPIO_InitStructure; //Pin TX GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5; GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF_PP; GPIO_Init(GPIOD, &GPIO_InitStructure); //Pin RX GPIO_PinRemapConfig(GPIO_Remap_USART2,ENABLE); GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6; GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN_FLOATING; GPIO_Init(GPIOD, &GPIO_InitStructure); 
 USART_InitTypeDef USART_InitStructure; USART_DeInit(USART2); 
 USART_InitStructure.USART_BaudRate = 9600; USART_InitStructure.USART_WordLength = USART_WordLength_8b; USART_InitStructure.USART_StopBits = USART_StopBits_1; USART_InitStructure.USART_Parity = USART_Parity_No; USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None; USART_InitStructure.USART_Mode = USART_Mode_Tx | USART_Mode_Rx; USART_Init(USART2, &USART_InitStructure); 
 USART_Cmd(USART2, ENABLE); 
 
 

Then periodically i use

USART_SendData(USART2,c)

Make sure you enable the APB clocks for USART2, GPIOD and AFIO. The latter is required for remapping to work.

apb1 for usart2 and apb2 for gpiod and afio were enabled. The problem was that i'm a douche :D, because i tried to scope the output with a simple tester, not considering that with 9600bps i could not see anything different than 3.3V;

Now another question if you don't mind: i would like to connect the comstick to a gsm module via uart. Electrical features of the module require CMOS 2.8V, and i read on stm32f107 datasheet that gpio are compliant with TTL and CMOS. So electrically i think that they can be connected directly without any serial level converter. So i did... but it does not work. Consider that the gsm module ha autorate, so i exclude problems about rating, stopbit, parity, etc..

Have you any ideas of what could be the problem? Thx in advantage