pHAT Module Series

pHAT-RV Technical Description

pHAT-RV Technical Description

Page 14 of 27

3.7.3 I

2C Registers

To write individual registers a device write must be undertaken by the Raspberry-Pi which

consists of a Start condition, device ID (‘D’ bit cleared), register to start write, one or more

bytes of data to be written and a stop condition (see Figure 2 for I

2C write protocol).

To read individual data and status registers a device write then read must be undertaken by

the Raspberry-Pi which consists of a Start condition, device ID (‘D’ bit clear), register to start

read and a Stop condition.

This is followed by a read, which consists of a Start condition, device ID (‘D‘ bit set), followed

by data from the register specified and terminated with a Stop condition. The RV also auto

increments the register specified for every additional read requested by the Master I

2C

device, which allows more than one register to be read in one transaction. This allows for

example Register 0 to Register 5, current UTC time, to be read in one transaction (see Figure 3

for I

2C read protocol).

There are 25 individual registers that can be written and 8 registers that can be read within

the RV as follows:

Table 5: I

2C Registers

Register name

Type

Register address

Description

Hex

Binary

Register address

w

00

00000000

Start register to write to

Stepper 1 control

w

01

00000001

Stepper motor 1 control

U

U U

E

D

C

B

A

A = Operate (0 - Stepper disabled 1

- Stepper enabled)

B = Reverse (0 - Stepper normal 1 -

Stepper reversed)

C = Rotate (0 - Single step 1 -

Constant rotation)

D = Step (0 - Normal step 1 - Half

step)

E = Hold (0 - No hold on stop 1 -

Hold on stop)

U = Unused

Stepper 1 steps MSB

w

02

00000010

Number of steps MSB

Stepper 1 steps LSB

w

03

00000011

Number of steps LSB

Stepper 1 speed

w

04

00000100

Step speed in quarter mS

(0.25mS)