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