- Thu Dec 04, 2014 6:49 pm
#4016
Hello, everybody.
I made additional test with i2c and Lua.
I bought PCF8591, which is an 8-bit 4-channel ADC + 8-bit 1-channel DAC.
I connected it using the attached schematics and wrote 2 simple scripts - one for outputing semi-triangle signal using DAC and one for reading first ADC channel.
DAC.lua
This code works using timer interrupt, raising/lowering the value of DAC (register 0x40) for PCF8591 (address 0x48).
ADC.lua
This code reads the ADC value of channel 1 (register 0x00) for 100 iterations, 4 times per second. The results are 2 - the ADC performs 2 approximation per 1 reading. When changing the potentiometer, one can see the first value is read before the second one. It is just fun to see the change of values.
Enjoy the code, let me know if it works for you.
I'll try also different/better i2c ADC devices as soon as I get the samples.
Schematics of ESP8266 connected to PCF8591
I made additional test with i2c and Lua.
I bought PCF8591, which is an 8-bit 4-channel ADC + 8-bit 1-channel DAC.
I connected it using the attached schematics and wrote 2 simple scripts - one for outputing semi-triangle signal using DAC and one for reading first ADC channel.
DAC.lua
Code: Select all
id=0
sda=8
scl=9
-- initialize i2c, set pin1 as sda, set pin0 as scl
i2c.setup(id,sda,scl,i2c.SLOW)
function write_reg(dev_addr, reg_addr, reg_val)
i2c.start(id)
i2c.address(id, dev_addr, i2c.TRANSMITTER)
i2c.write(id, reg_addr)
i2c.write(id, reg_val)
i2c.stop(id)
end
-- address of adc PCF8591
device=0x48 --72 decimal
i = 1
dir = 1
tmr.alarm(150,1,function()
write_reg(device, 0x40, i)
dir = (i == 0) and (dir == -1) and 1 or (i == 255) and (dir == 1) and -1 or dir
i = i + dir
end
)
This code works using timer interrupt, raising/lowering the value of DAC (register 0x40) for PCF8591 (address 0x48).
ADC.lua
Code: Select all
id=0
sda=8
scl=9
-- initialize i2c, set pin1 as sda, set pin0 as scl
i2c.setup(id,sda,scl,i2c.SLOW)
-- user defined function: read from reg_addr content of dev_addr
function read_reg(dev_addr, reg_addr)
i2c.start(id)
i2c.address(id, dev_addr ,i2c.TRANSMITTER)
i2c.write(id,reg_addr)
i2c.stop(id)
i2c.start(id)
i2c.address(id, dev_addr,i2c.RECEIVER)
c=i2c.read(id,2)
i2c.stop(id)
return c
end
function write_reg(dev_addr, reg_addr, reg_val)
i2c.start(id)
i2c.address(id, dev_addr, i2c.TRANSMITTER)
i2c.write(id, reg_addr)
i2c.write(id, reg_val)
i2c.stop(id)
end
-- address of adc PCF8591
device=0x48 --72 decimal
for i=0,100 do
result = read_reg(device, 0x00)
print("Result: " .. string.byte(result, 1) .. " " .. string.byte(result, 2))
tmr.delay(250000)
tmr.wdclr()
end
This code reads the ADC value of channel 1 (register 0x00) for 100 iterations, 4 times per second. The results are 2 - the ADC performs 2 approximation per 1 reading. When changing the potentiometer, one can see the first value is read before the second one. It is just fun to see the change of values.
Enjoy the code, let me know if it works for you.
I'll try also different/better i2c ADC devices as soon as I get the samples.
