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fmcdio_vhdci_eem: cleanup and document

This commit is contained in:
Sebastien Bourdeauducq 2018-07-20 09:54:20 +08:00
parent d152506ecb
commit cab0ba408d
1 changed files with 12 additions and 9 deletions
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21
artiq/coredevice/fmcdio_vhdci_eem.py
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@ -1,3 +1,5 @@
# Definitions for using the "FMC DIO 32ch LVDS a" card with the VHDCI-EEM breakout v1.1
eem_fmc_connections = {
0: [0, 8, 2, 3, 4, 5, 6, 7],
1: [1, 9, 10, 11, 12, 13, 14, 15],
@ -6,20 +8,21 @@ eem_fmc_connections = {
}
fmcdio_shiftreg_permutation = [
1, 0, 3, 2, 5, 4, 7, 6,
9, 8, 11, 10, 13, 12, 15, 14,
17, 16, 19, 18, 21, 20, 23, 22,
25, 24, 27, 26, 29, 28, 31, 30
]
def shiftreg_bits(eem, out_pins):
"""
Returns the bits that have to be set in the FMC card direction
shift register for the given EEM.
Takes a set of pin numbers (0-7) at the EEM. Return values
of this function for different EEMs should be ORed together.
"""
r = 0
for i in range(8):
if i not in out_pins:
lvds_line = eem_fmc_connections[eem][i]
shift = fmcdio_shiftreg_permutation.index(lvds_line)
# lines are swapped in pairs to ease PCB routing
# at the shift register
shift = lvds_line ^ 1
r |= 1 << shift
return r