solving servo jittering when combine with i2c devices

[muhammadhusni777]

hey anyone know how to remove sensor jittering when using i2c devices. i use STM32F429ZI, servo, and ads1115. if i only use stm32 and servo it works properly, but when i add ads1115 it start jittering. please help me, thank you

[ABOSTM]

Hi @muhammadhusni777 ,
I guess you face real time issue, linked to preemption of servo by I2C:
Servo library is based on HardwareTimer, and it uses Interrupts to change servo pin state.
The interrupt priority of HardwareTimer (and of Servo) is by default defined to:
#define TIM_IRQ_PRIO 3
In parallel, you have your I2C component for which interrupt priority is by default defined to:
#define I2C_IRQ_PRIO 2

Lowest value means higher priority, so I2C has higher priority and will preempt servo. And if I2C traffic is too intensive (or too long, ...) it could impact/delay servo pin state change and thus induce jittering.

So you can try either to:

• invert priorities by redefining TIM_IRQ_PRIO and I2C_IRQ_PRIO (recommended)
• reduce I2C traffic by reducing for example ADC sampling frequency