add dac_test
add dac_test

pavel-demin/red-pitaya-notes,pavel-demin/red-pitaya-notes,pavel-demin/red-pitaya-notes,pavel-demin/red-pitaya-notes,fbalakirev/red-pitaya-notes,fbalakirev/red-pitaya-notes,fbalakirev/red-pitaya-notes,pavel-demin/red-pitaya-notes,pavel-demin/red-pitaya-notes,fbalakirev/red-pitaya-notes,pavel-demin/red-pitaya-notes,fbalakirev/red-pitaya-notes,fbalakirev/red-pitaya-notes,pavel-demin/red-pitaya-notes,fbalakirev/red-pitaya-notes