What is "PCA9629" ?¶

A Stepper motor controller¶

PCA9629 (x5) demo board: PCA9629, 4x FETs and stepper motor

The PCA9629 is an I2C-bus controlled low-power CMOS device that provides all the logic and control required to drive a four phase stepper motor. PCA9629 is intended to be used with external high current drivers to drive the motor coils. The PCA9629 supports three stepper motor drive formats: one-phase (wave drive), two-phase, and half-step. In addition, when used as inputs, four General Purpose Input/Outputs (GPIOs) allow sensing of logic level output from optical interrupter modules and generate active LOW interrupt signal on the INT pin of PCA9629. This is a useful feature in sensing home position of motor shaft or reference for step pulses. Upon interrupt, the PCA9629 can be programmed to automatically stop the motor or reverse the direction of rotation of motor.

Communicate with mbed through I2C. The motor can be operated by register settings

Output wave train is programmable using control registers. The control registers are programmed via the I2C-bus. Features built into the PCA9629 provide highly flexible control of stepper motor, off-load bus master/micro and significantly reduce I2C-bus traffic. These include control of step size, number of steps per single command, number of full rotations and direction of rotation. A ramp-up on start and/or ramp-down on stop is also provided.

Waveforms: Lower 2 lines are I2C bus. Upper 4 lines are output for motor driver stage
Motor moving 16 steps with acceleration and deceleration after register setting via I2C

The PCA9629 is available in a 16-pin TSSOP package and is specified over the -40 deg-C to +85 deg-C industrial temperature range.

TSSOP16 package

Datasheet is available at next URL.
http://www.nxp.com/documents/data_sheet/PCA9629.pdf

Sample code¶

This sample code operates the PCA9629 using its library. The library is available here.

This program targets PCA9629 which has I2C address of 0c42 on I2C bus on pin28 and pin27 of mbed. 4 types motor actions are demonstrated in sequence (following 1..4 steps in loop).

1. Simple motor turn demo
   • Motor moved 96 steps with 100pps (pulse persecond) speed
   • Then the motor turn reversed, move 48 steps by 50pps.
2. Ramp control demo
   • total operation time = 2 seconds, initial speed = 40.69pps, rotations = 5turns+0steps, ramp-up enable = enable, ramp-down enable = enable, rotate direction = CW
   • The ramp control can be done with several register settings. The setting value calculation can be done by register setting tool (an Excel worksheet) from NXP.
3. Auto interrupt demo
   • The GPIO inputs can be used as interrupt for PCA9629. The operation can be stopped or change the direction of turn.
   • This is turn direction auto reversing demo. Motor will switch the direction 12 steps after interrupt signal assertion.
   • The register setting of interrupt operation can be done by register setting tool also.
4. Speed change demo
   • Changing motor speed in 5 steps from 55pps to 275pps.