# FMU-v5 and libuavcan CAN buses quantity are different

**URL:** <https://discuss.px4.io/t/fmu-v5-and-libuavcan-can-buses-quantity-are-different/10456>\
**Category:** Uncategorized\
**Created:** [April 12, 2019, 1:00pm UTC](https://discuss.px4.io/t/fmu-v5-and-libuavcan-can-buses-quantity-are-different/10456 "2019-04-12T13:00:07Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![sevg](https://discuss.px4.io/user_avatar/discuss.px4.io/sevg/32/3802_2.png) [@sevg](https://discuss.px4.io/u/sevg)\
**Post date:** [April 12, 2019, 1:00pm UTC](https://discuss.px4.io/t/fmu-v5-and-libuavcan-can-buses-quantity-are-different/10456/1 "2019-04-12T13:00:07Z")

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Hello. I really confused with quantity of available CAN buses in FMU-v5.  
I clearly see, that FMU-v5 source code defines all 3 CANs at STM32F7.  
` #define GPIO_CAN1_RX GPIO_CAN1_RX_5 /* PI9 */ #define GPIO_CAN1_TX GPIO_CAN1_TX_4 /* PH13 */ #define GPIO_CAN2_RX GPIO_CAN2_RX_1 /* PB12 */ #define GPIO_CAN2_TX GPIO_CAN2_TX_1 /* PB13 */ #define GPIO_CAN3_RX GPIO_CAN3_RX_1 /* PA8 */ #define GPIO_CAN3_TX GPIO_CAN3_TX_1 /* PA15 */`  
and defines UAVCAN\_STM32\_NUM\_IFACES =2  
But also I see, that libuavcan allows set only 2 CANs, described with UAVCAN\_STM32\_NUM\_IFACES. This cannot contain value “3” (for CAN3 if we want). But FMU-v5 code initializes all 3 CANs… Or FMU-v5 code dont works and it really releases only 2 CANs???  
Hence  
`#define GPIO_CAN3_RX GPIO_CAN3_RX_1 `  
is fail and unused…  
Right??