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Support readback in SU-Servo mode via MISO #7

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sb10q merged 2 commits from occheung/urukul-pld:readback into master 2025-10-31 09:03:39 +08:00
Conversation 2 Commits 2 Files Changed 2 +75 -31
occheung commented 2025-10-10 17:05:54 +08:00
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This PR changes the pin mapping in SU-Servo mode.

  • MISO pin is assigned EEM0[2], identical to non-servo mode.
  • NU_CLK is moved to EEM0[5] to make way for MISO.
  • NU_CS pin is removed. CS_N is now simply pulled low when in servo mode, as permitted by the AD9910 datasheet.
    Only PROTO_REV 9 firmware, on either Xilinx CoolRunner II CPLD (xc2c) or iCE40 targets, will receives this change.

Closes #6.

This PR changes the pin mapping in SU-Servo mode. - MISO pin is assigned EEM0[2], identical to non-servo mode. - NU_CLK is moved to EEM0[5] to make way for MISO. - NU_CS pin is removed. CS_N is now simply pulled low when in servo mode, as permitted by the AD9910 datasheet. Only PROTO_REV 9 firmware, on either Xilinx CoolRunner II CPLD (xc2c) or iCE40 targets, will receives this change. Closes #6.
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occheung added 2 commits 2025-10-10 17:05:55 +08:00
assign MISO to EEM[2] regardless of mode 3db2d54d01
dds: always select DDS when in servo mode f0a8602302
occheung added 3 commits 2025-10-14 13:42:36 +08:00
update MISO docs 7f2ab184c0
docs: remove NU_CS mentions a4076f6828
mention readback possibility on top of MASK_NU 2b5b387acf
occheung force-pushed readback from 2b5b387acf to d14eba7311 2025-10-14 16:59:21 +08:00 Compare
occheung changed title from WIP: Support readback in SU-Servo mode via MISO to Support readback in SU-Servo mode via MISO 2025-10-14 16:59:34 +08:00
mwojcik reviewed 2025-10-15 13:48:27 +08:00
xc2c/urukul.py
@@ -285,1 +287,4 @@
With CS = 3, MASK_NU selects the source of MISO among the 4 DDS available.
| MASK_NU | MISO Source |
mwojcik commented 2025-10-15 13:48:27 +08:00
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nit: it's more of a select (one from 4), rather than a mask (any of 4), although I understand the desire not to change the original signal name

nit: it's more of a select (one from 4), rather than a mask (any of 4), although I understand the desire not to change the original signal name
dpn commented 2025-10-29 21:00:00 +08:00
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I haven't tested this, but it seems altogether like a cleaner solution than the very limited half-duplex shift-register mode we use in Oxford (though we were constrained to also work on old CPLD versions and rev. 8, and didn't spot that we could steal one of the DDS diff pair lines). Assuming it works reliably in testing, just having straightforward readback via regular MISO seems as implemented here seems like the way to go.

I haven't tested this, but it seems altogether like a cleaner solution than the very limited half-duplex shift-register mode we use in Oxford (though we were constrained to also work on old CPLD versions and rev. 8, and didn't spot that we could steal one of the DDS diff pair lines). Assuming it works reliably in testing, just having straightforward readback via regular MISO seems as implemented here seems like the way to go.
sb10q merged commit d14eba7311 into master 2025-10-31 09:03:39 +08:00
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Reference: M-Labs/urukul-pld#7
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