Update README.md

Author: mphhpm

README.md

@@ -1,10 +1,19 @@
 # stm32-pwm
 ```
-generates a pwm signal on a gpio pin using tim1 and dma on a blackpill board
-libopencm3 is being used as HAL
+pwm signal on a gpio pin using tim1 and dma on a blackpill board stm32f401 
+libopencm3 as HAL
 ```
 ## Helpful documents
 ```
 RM 0368 Reference manual STM32F401xB/C and STM32F401xD/E advanced Arm®-based 32-bit MCUs
 STM32F401xB STM32F401xC Arm® Cortex®-M4 32-bit MCU+FPU, 105 DMIPS, 256KB Flash / 64KB RAM, 11 TIMs, 1 ADC, 11 comm. interfaces
 ```
+
+## Tools ##
+```
+os : windows
+make, gcc & friends : https://xpack.github.io/dev-tools/arm-none-eabi-gcc
+ide : https://www.eclipse.org
+shell : https://www.cygwin.com
+st-link : https://www.st.com/en/development-tools/st-link-v2.html, alixepress
+```