因为控制屏的使能线没有控制信号了，屏当然不亮。

在STM32手册里，待机模式这样说的，

5.3.6 Standby mode
The Standby mode allows to achieve the lowest power consumption. It is based on the
Cortex®-M4 with FPU deepsleep mode, with the voltage regulator disabled. The 1.2 V
domain is consequently powered off. The PLLs, the HSI oscillator and the HSE oscillator are
also switched off. SRAM and register contents are lost except for registers in the backup
domain (RTC registers, RTC backup register and backup SRAM), and Standby circuitry (see
Figure 9)


待机模式
待机模式下可达到最低功耗。待机模式基于 Cortex™-M4F 深度睡眠模式，其中调压器被禁
止。因此 1.2 V 域断电。 PLL、 HSI 振荡器和 HSE 振荡器也将关闭。除备份域（RTC 寄存
器、 RTC 备份寄存器和备份 SRAM）和待机电路中的寄存器外， SRAM 和寄存器内容都将
丢失（参见图 7）