BBB has 12‐bit ADCs (2^12 = 4,096), meaning a value between 0 and 2^12 − 1 (0 to 4,095), read() should return the raw value devide by 4095.

Deng Bo · Deng Bo · commit 9220c13f9070 · 2016-10-26T11:23:07.000+08:00
diff --git a/source/py_adc.c b/source/py_adc.c
@@ -86,7 +86,7 @@ static PyObject *py_read(PyObject *self, PyObject *args)
     }
 
     //scale modifier
-    value = value / 1800.0;
+    value = value / 4095.0;
 
     py_value = Py_BuildValue("f", value);
 

Original file line number	Diff line number	Diff line change
`@@ -86,7 +86,7 @@ static PyObject py_read(PyObject self, PyObject *args)`
`86`	`86`	`}`
`87`	`87`
`88`	`88`	`//scale modifier`
`89`		`- value = value / 1800.0;`
	`89`	`+ value = value / 4095.0;`
`90`	`90`
`91`	`91`	`py_value = Py_BuildValue("f", value);`
`92`	`92`