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