63 lines
1.7 KiB
Lua
63 lines
1.7 KiB
Lua
-- Walk the ADC through a stepped triangle wave using the attached voltage
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-- divider and I2C GPIO expander.
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local N = ...
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N = (N or require "NTest")("adc-env")
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-- TODO: Preflight test that we are in the correct environment with an I2C
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-- expander in the right place with the right connections.
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-- TODO: Use the mcp23017 module in the main tree rather than hand-coding
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-- the commands
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N.test('setup', function()
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-- Configure the ADC
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if adc.force_init_mode(adc.INIT_ADC)
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then
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node.restart()
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error "Must reboot to get to ADC mode"
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end
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-- Configure the I2C bus
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i2c.setup(0, 2, 1, i2c.FAST)
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-- Set the IO expander port B to channels 0 and 1 as outputs
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i2c.start(0)
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ok(i2c.address(0, 0x20, i2c.TRANSMITTER))
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i2c.write(0, 0x01, 0xFC)
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i2c.stop(0)
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end)
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-- set the two-bit voltage divider output value to v (in 0,1,2,3)
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local function setv(v)
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assert (0 <= v and v <= 3)
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i2c.start(0)
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i2c.address(0, 0x20, i2c.TRANSMITTER)
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i2c.write(0, 0x15, v)
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i2c.stop(0)
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end
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-- read out the ADC and compare to given range
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local function checkadc(min, max)
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local v = adc.read(0)
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return ok(min <= v and v <= max, ("read adc: %d <= %d <= %d"):format(min,v,max))
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end
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-- Since we have a rail-to-rail 4-tap DAC, as it were, give us some one-sided
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-- wiggle around either rail and some two-sided wiggle around both middle stops
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local vmin = { 0, 300, 700, 1000 }
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local vmax = { 24, 400, 800, 1024 }
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-- Set the DAC, wait a brief while for physics, and then read the ADC
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local function mktest(fs, i)
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N.test(fs:format(i), function()
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setv(i)
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tmr.delay(10)
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checkadc(vmin[i+1], vmax[i+1])
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end)
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end
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-- test all four stops on the way up, and the three to come back down
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for i=0,3 do mktest("%d up", i) end
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for i=2,0,-1 do mktest("%d down", i) end
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