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ad9910: add docs for sync tuning, refactor 

Signed-off-by: Robert Jördens <rj@quartiq.de>
This commit is contained in:
Robert Jördens 2018-10-26 15:42:42 +00:00
parent 8a47a6b2fb
commit 7b92282012
1 changed files with 45 additions and 7 deletions
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52
artiq/coredevice/ad9910.py
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@ -150,7 +150,7 @@ class AD9910:
raise ValueError("Urukul AD9910 AUX_DAC mismatch")
delay(50*us) # slack
# Configure PLL settings and bring up PLL
self.write32(_AD9910_REG_CFR2, 0x01000020)
self.write32(_AD9910_REG_CFR2, 0x01010020)
self.cpld.io_update.pulse(1*us)
cfr3 = (0x0807c100 | (self.pll_vco << 24) |
(self.pll_cp << 19) | (self.pll_n << 1))
@ -256,22 +256,53 @@ class AD9910:
self.cpld.cfg_sw(self.chip_select - 4, state)
@kernel
def set_sync(self, in_delay, window, preset=0):
def set_sync(self, in_delay, window):
"""Set the relevant parameters in the multi device synchronization
register. See the AD9910 datasheet for details. The SYNC clock
generator preset value is set to zero, and the SYNC_OUT generator is
disabled.
:param in_delay: SYNC_IN delay tap (0-31) in steps of ~75ps
:param window: Symmetric SYNC_IN validation window (0-15) in
steps of ~75ps for both hold and setup margin.
"""
self.write32(_AD9910_REG_MSYNC,
(window << 28) | # SYNC S/H validation delay
(1 << 27) | # SYNC receiver enable
(0 << 26) | # SYNC generator disable
(0 << 25) | # SYNC generator SYS rising edge
(preset << 18) | # SYNC preset
(0 << 18) | # SYNC preset
(0 << 11) | # SYNC output delay
(in_delay << 3)) # SYNC receiver delay
self.write32(_AD9910_REG_CFR2, 0x01000020) # clear SMP_ERR
@kernel
def clear_smp_err(self):
"""Clears the SMP_ERR flag and enables SMP_ERR validity monitoring.
Violations of the SYNC_IN sample and hold margins will result in
SMP_ERR being asserted. This then also activates the red LED on
the respective Urukul channel.
Also modifies CFR2.
"""
self.write32(_AD9910_REG_CFR2, 0x01010020) # clear SMP_ERR
self.cpld.io_update.pulse(1*us)
self.write32(_AD9910_REG_CFR2, 0x01000000) # enable SMP_ERR
self.write32(_AD9910_REG_CFR2, 0x01010000) # enable SMP_ERR
self.cpld.io_update.pulse(1*us)
@kernel
def tune_sync_delay(self):
"""Find a stable SYNC_IN delay.
This method first locates the smallest SYNC_IN validity window at
minimum window size and then increases the window a bit to provide some
slack and stability.
It starts scanning delays around :attr:`sync_delay_seed` (see the
device database arguments and :meth:`__init__`) at maximum validation window
size and decreases the window size until a valid delay is found.
:return: Tuple of optimal delay and window size.
"""
dt = 14 # 1/(f_SYSCLK*75ps) taps per SYSCLK period
max_delay = dt # 14*75ps > 1ns
max_window = dt//4 + 1 # 2*75ps*4 = 600ps high > 1ns/2
@ -282,8 +313,13 @@ class AD9910:
# alternate search direction around seed_delay
if in_delay & 1:
in_delay = -in_delay
in_delay = (self.sync_delay_seed + (in_delay >> 1)) & 0x1f
in_delay = self.sync_delay_seed + (in_delay >> 1)
if in_delay < 0:
in_delay = 0
elif in_delay > 31:
in_delay = 31
self.set_sync(in_delay, window)
self.clear_smp_err()
# integrate SMP_ERR statistics for a few hundred cycles
delay(10*us)
err = urukul_sta_smp_err(self.cpld.sta_read())
@ -292,5 +328,7 @@ class AD9910:
if not err:
window -= min_window # add margin
self.set_sync(in_delay, window)
return window, in_delay
self.clear_smp_err()
delay(40*us) # slack
return in_delay, window
raise ValueError("no valid window/delay")