STM32F4 Timer Internal Trigger Connection

/*
 * Trigger select mapping for slave timer from master timer.  This is
 * unfortunately not very straightforward; there‘s no tidy way to do this
 * algorithmically.  To avoid burning memory for a lookup table, use macros to
 * compute the offset.  This also has the benefit that compilation will fail if
 * an unsupported master/slave pairing is used.
 *
 * Slave        Master
 *     1    15  2  3  4  (STM32F100 only)
 *     2     9 10  3  4
 *     3     9  2 11  4
 *     4    10  2  3  9
 *     9     2  3 10 11  (STM32L15x only)
 *     --------------------
 *     ts =  0  1  2  3
 */
#define STM32_TIM_TS_SLAVE_1_MASTER_15 0
#define STM32_TIM_TS_SLAVE_1_MASTER_2  1
#define STM32_TIM_TS_SLAVE_1_MASTER_3  2
#define STM32_TIM_TS_SLAVE_1_MASTER_4  3
#define STM32_TIM_TS_SLAVE_2_MASTER_9  0
#define STM32_TIM_TS_SLAVE_2_MASTER_10 1
#define STM32_TIM_TS_SLAVE_2_MASTER_3  2
#define STM32_TIM_TS_SLAVE_2_MASTER_4  3
#define STM32_TIM_TS_SLAVE_3_MASTER_9  0
#define STM32_TIM_TS_SLAVE_3_MASTER_2  1
#define STM32_TIM_TS_SLAVE_3_MASTER_11 2
#define STM32_TIM_TS_SLAVE_3_MASTER_4  3
#define STM32_TIM_TS_SLAVE_4_MASTER_10 0
#define STM32_TIM_TS_SLAVE_4_MASTER_2  1
#define STM32_TIM_TS_SLAVE_4_MASTER_3  2
#define STM32_TIM_TS_SLAVE_4_MASTER_9  3
#define STM32_TIM_TS_SLAVE_9_MASTER_2  0
#define STM32_TIM_TS_SLAVE_9_MASTER_3  1
#define STM32_TIM_TS_SLAVE_9_MASTER_10 2
#define STM32_TIM_TS_SLAVE_9_MASTER_11 3