Generic I2C Interface

Before start coding you need to setup I2C on the Raspberry Pi. Please following these instructions.

I2C Pins

Library

Access the basic I2C command with the library i2c:

import i2c

Function Reference

Open device

id = Open(address)
id = Open(address, interface)

Open a connected I2C device with address address on I2C interface interface. interface is an optional parameter. Several devices can be opened. id will be used to identify the device.

• address
  • Integer: 0 … 127
  • I2C device address
• interface
  • String
  • I2C interface name
  • Optional parameter. Default value is /dev/i2c-1
• id
  • Device id

Example:

id = open(0x55)
id = open(0x55, "/dev/i2c-1")

Close device

Close(id)

When closing a SmallBASIC program, I2C access will be automatically closed. If you want to manually close I2C access for the device with device id id, use this function.

• id
  • Device id

Write to I2C device

Write(id, dataByte)
Write(id, dataArray)

Send one byte dataByte or an 1d array dataArray of bytes to the devices with device id id.

• id
  • Device id
• dataByte
  • Integer: 0 … 255
  • One byte of data
• dataArray
  • 1D-array of integers [0 … 255, 0 … 255, … ]
  • Array of byte data

Example:

Write(id, 0x20)
Write(id, [0x20, 0x21, 0xA3])

Write to register of a I2C device

WriteReg(id, reg, dataByte)
WriteReg(id, reg, dataArray)

Send one byte dataByte or an 1d array dataBytes of bytes to the devices with device id id.

• id
  • Device id
• reg
  • Integer: 0 … 255
  • Device register
• dataByte
  • Integer: 0 … 255
  • One byte of data
• dataArray
  • 1D-array of integers [0 … 255, 0 … 255, … ]
  • Array of byte data

Example:

WriteReg(id, 0x05, 0x20)
WriteReg(id, 0x05, [0x20, 0x21, 0xA3])

Read from I2C device

res = Read(id)
res = Read(id, bytes)

Read number of bytes bytes from the device with device id id. bytes is an optional parameter.

• id
  • Device id
• bytes
  • Integer
  • Number of bytes to read from device
  • Optional paramater. Default value is 1
• res
  • Integer or 1d-array of integer
  • Data read from device
  • If more than 1 byte is read, res is an 1d array.

Read register of I2C device

res = Read(id, reg)
res = Read(id, reg, bytes)

Read number of bytes bytes from the register reg of the device with device id id. bytes is an optional parameter.

• id
  • Device id
• reg
  • Integer: 0 … 255
  • Device register
• bytes
  • Integer
  • Number of bytes to read from device.
  • Optional paramaeter. Default value is 1
• res
  • Integer or 1d-array of integer
  • Data read from device
  • If more than 1 byte is read, res is an 1d array.

Example:

res = ReadReg(id, 0x05)       ' Read one byte from register 0x05
res = ReadReg(id, 0x05, 5)    ' Read five bytes from register 0x05

Read byte from SMBus device

res = SmbusReadByte(id, reg)

Read one byte from the register reg of the SMBus device with device id id.

• id
  • Device id
• reg
  • Integer: 0 … 255
  • Device register
• res
  • Integer: 0 … 255
  • Data read from device

Example:

res = SmbusReadByte(id, 0x05)       ' Read one byte from register 0x05

Read word from SMBus device

res = SmbusReadWord(id, reg)

Read one word (2 bytes) from the register reg of the SMBus device with device id id.

• id
  • Device id
• reg
  • Integer: 0 … 255
  • Device register
• res
  • Integer: 0 … 65535
  • Data read from device

Example:

res = SmbusReadWord(id, 0x05)       ' Read one byte from register 0x05

Write byte to SMBus device

SmbusWriteByte(id, reg, data)

Send one byte to the register reg of the SMBus device with device id id.

• id
  • Device id
• reg
  • Integer: 0 … 255
  • Device register
• data
  • Integer: 0 … 255
  • One byte of data

Example:

SmbusWriteByte(id, 0x05, 0xA2)       ' Write 0xA2 to register 0x05

Write word to SMBus device

SmbusWriteWord(id, reg, data)

Send one word (2 bytes) to the register reg of the SMBus device with device id id.

• id
  • Device id
• reg
  • Integer: 0 … 255
  • Device register
• data
  • Integer: 0 … 65535
  • Two byte of data

Example:

SmbusWriteWord(id, 0x05, 0xA202)       ' Write 0xA202 to register 0x05

Example Code

1. BH1750 - Ambient Light Sensor

Please be careful, the sensors are usually driven with 3.3V. The sensor from Adafruit can be driven with 3.3V or 5V. If you don’t connect the address pin, then the sensor will use address 0x23.

import i2c

Print "Connect to BH1750"

sensor = i2c.Open(0x23, "/dev/i2c-1")

' Power down
i2c.write(sensor, 0x00)
' Power on
i2c.write(sensor, 0x01)
delay(1000)

' Read one time with low resolution
d = i2c.ReadReg(sensor, 0x23, 2)
ValueLowRes = ((d[0] lshift 8) BOR d[1]) / 1.2
delay(1000)

' Read one time with high resolution
d = i2c.ReadReg(sensor, 0x20, 2)
ValueHighRes = ((d[0] lshift 8) BOR d[1]) / 1.2

print "Low resolution : " + ValueLowRes  + " lx"
print "High resolution: " + valueHighRes + " lx"

2. PiSugar 3 Plus - Power Supply

import i2c

Print "Access PiSugar 3 Plus"

PiSugar = i2c.Open(0x57, "/dev/i2c-1")

ChargeStatus = i2c.SmbusReadByte(PiSugar, 0x2A)
print ChargeStatus; "%"

VoltageHigh = i2c.SmbusReadByte(PiSugar, 0x22)
VoltageLow = i2c.SmbusReadByte(PiSugar, 0x23)
Voltage = (VoltageHigh lshift 8) + VoltageLow
print Voltage; "mV"

IsPowerConnected = i2c.SmbusReadByte(PiSugar, 0x02) rshift 7
print "USB Power connected: "; IsPowerConnected

print "Seconds of RTC: "; i2c.SmbusReadByte(PiSugar, 0x37)