BH1750 Module

This Lua module provides access to the BH1750 ambient light sensor for the NodeMCU firmware.

The module is created for the float version of the NodeMCU and requires i2c and bit C modules built into the firmware.

Example

bh1750 = require("bh1750")

I2C_ID = 0
I2C_SCL_PIN = 5
I2C_SDA_PIN = 6

if i2c.setup(I2C_ID, I2C_SDA_PIN, I2C_SCL_PIN, i2c.SLOW) == 0 then
  print("[DEBUG] Failed to initialize the I2C bus")
end

cfg = {}
cfg.i2c_id      = I2C_ID

m = bh1750.setup(cfg)
if not m then
  print("[DEBUG] Setup failed")
  m = nil
  bh1750 = nil
  package.loaded["bh1750"] = nil
  return
end

tmr.create():alarm(1000, tmr.ALARM_AUTO, function()
  local c = m:get_counts()
  local l = m:get_value()
  if c and l then
    print(l .. " lx / " .. c .. " counts")
  end
end)

bh1750.setup()

Configure the BT1750 module.

Syntax

bh1750.setup(cfg)

Parameters

• cfg table containing configuration data:
  • i2c_id i2c bus number
  • address device address (default: 0x23):
    • 0x23 ADDR pin voltage <= 0.3*VCC
    • 0x5C ADDR pin voltage >= 0.7*VCC
  • mode measurement mode (default: 0x10)
  • mtreg MTreg value (default: 69)

Returns

BH1750 object obj on success, nil on error.

See also

• obj:set_mode()
• obj:set_mtreg()

obj:get_counts()

Read raw brightness value.

Syntax

obj:get_counts()

Returns

Raw brightness value in counts or nil on error.

obj:get_value()

Read brightness value.

Syntax

obj:get_value()

Returns

Brightness value in lux or nil on error.

obj:reset()

Reset the data register stop measurements. Device should be in the power_on state.

See also

• obj:set_mode()
• obj:set_state()

Syntax

obj:reset()

Returns

true on success, nil on error.

obj:set_mode()

Set measurement mode.

Syntax

obj:set_mode(mode)

Parameters

• mode measurement mode (default: 0x10):
  • 0x10 continuous H-res (1 lx resolution, 120 ms measurement time)
  • 0x11 continuous H-res 2 (0.5 lx resolution, 120 ms measurement time)
  • 0x13 continuous L-res (4 lx resolution, 16 ms measurement time)
  • 0x20 one-time H-res (1 lx resolution, 120 ms measurement time)
  • 0x21 one-time H-res 2 (0.5 lx resolution, 120 ms measurement time)
  • 0x23 one-time L-res (4 lx resolution, 16 ms measurement time)

Returns

true on success, nil on error.

obj:set_mtreg()

Set value of the measurement time register (MTreg).

Syntax

obj:set_mtreg(mt)

Parameters

mt MTreg value (31~254, default: 69)

Returns

true on success, nil on error.

obj:set_state()

Set the state of the device.

Syntax

obj:set_state(command)

Parameters

• command change state:
  • 0 power down, measurements are stopped
  • 1 power up, enter the power_on state

Returns

true on success, nil on error.