AD9951 Unresponsive to SPI communication.

ssmith

on Nov 17, 2022

Category: Hardware

Product Number: AD9951

I am trying to confirm that my AD9951 is receiving SPI communication. I have not received any response to my commands (nothing coming back on the SPI line) and also cannot seem to make the chip do anything.

The simplest test I can think of is to reset the device, initialize, then enable the CrystalOut pin to see the clock being passed through. So far the chip is not responsive.

I initialize it, confirm the refclock in, write the CFR2 register, then see if the crystal out pin has anything coming out.

Hardware: Raspberry Pico running MicroPython

Schematic for ADD9951 Interface:

* NOTE: One change not reflected on the schematic is that the PWRDWNCTRL pin is now controlled by the pico instead of always pulled high.

Refclock in:

Initialization Code (MicroPython):

def __init__

# Set device pins default conditions

self._chipSelectDisable() #active low

self.reset_pin.low()

self.io_sync_pin.low()

self.io_update_pin.low()

# Device is active low for powerdown ctrl pin

self.pwrdwnctrl_pin.low()

utime.sleep_us(1)

# Reset Device

self._reset()

self._ioSync()

utime.sleep_us(10)

# Verify device initialized

err = self._checkDeviceResponse()

def _reset(self):

"""Resets Device

try:

self.reset_pin.high()

utime.sleep_us(10)

self.reset_pin.low()

except Exception as e:

print("ERROR : "+str(e))

def _checkDeviceResponse(self):

self.cfr2.raw = 0 # default reg val

self.cfr2.refclk_mult = 5 # 24Mhz refclock x 5 = 120 MHz sys clock

self.cfr2.vco_range = 0 # 100-250

self.cfr2.xtal_out_ena = 1

try:

error = self._writeRegister24Bit(REG_CFR2, self.cfr2.raw)

except Exception as e:

print("ERROR : "+str(e))

def _writeRegister24Bit(self, reg : int, data : int):

error = ERR_NONE

tx_buf_1 = bytearray(1)

try:

# Instruction format

cmd = AD9954_instruction_t()

cmd.read_ena = 0 # Write command

cmd.reg_addr = reg & AD9954_REGADDR_MASK

# Send read command with register address

tx_buf_1[0] = cmd.raw

tx_buf_3 = bytearray(3)

# MSB First

tx_buf_3[0] = AD9954_BYTE(data, 2) # (data >> 16u & 0xFFu);

tx_buf_3[1] = AD9954_BYTE(data, 1) # (data >> 8u & 0xFFu);

tx_buf_3[2] = AD9954_BYTE(data, 0) # (data >> 0u & 0xFFu);

self._chipSelectEnable()

self.spi_h.write(bytes(tx_buf_1))

self.spi_h.write(bytes(tx_buf_3))

self._chipSelectDisable()

self._ioUpdate() # store the data in the registers

except Exception as e:

print("ERROR WRITE REG 24BIT: "+str(e))

return error

SPI Settings: 100khz, CPOL/CPHA = 1

SPI Trace

xtalout ad9951 hardware spi refclk clock and timing Clocks & Timers add9951 Direct Digital Synthesis (DDS) Show More

Parents

Jules.Nikko

on Nov 21, 2022 11:37 AM
0
Hi ssmith ,

Have you tried checking out this guide on the things to be checked when using DDS evaluation board via external control? This might help you in this issue.

All the best,

Jules
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ssmith
on Nov 22, 2022 12:33 PM in reply to Jules.Nikko
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Hello Jules.Nikko,

It looks like "guide" is supposed to be a link, but when I click on it nothing happens. I would be interested in the guide! Can you redo the link or include the full path?
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Jules.Nikko

on Nov 22, 2022 1:39 PM in reply to ssmith
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Hi ssmith ,

Sorry about that. Here's the link.

All the best,

Jules
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ssmith
on Nov 22, 2022 2:17 PM in reply to Jules.Nikko
0
Hi Jules.Nikko ,

From the listed guide, here are the things I have checked.

This is the set-up in which the evaluation board is 100% to be controlled externally. The basic things to be checked are the following:

Most of the DDS evaluation boards have logic buffers between the USB interface and the DDS. There are jumpers that enable/disable these logic buffers. Locate for these jumpers and set to disable to tri-state the ICs on the evaluation board. The user may refer to the evaluation board schematic to easily identify these jumpers.

I'm not using an eval board.

Connect ALL the required input pins to the external circuitry via interface cable to control the DUT. Some critical inputs are the main_Reset and the external power down pins.

I'm controlling all input pins except for Loop Filter, which is not connected to anything. Sync_In is grounded.

Selecting the profile mode can be done two ways: hardwire each profile pin to logic 1 or 0, or connect interface cable from these pins to control it externally.

AD9951 doesn't have profile pins.

Set the Function Pins (applicable only to AD9914/AD9915) to the desired parallel-port configuration.

N/A for AD9951

Apply power, reference clock and control ALL digital inputs. When controlling the digital inputs, make sure that there is a defined logic state for each input. The external power down must be set to logic 0 to ensure the DDS is not in power-down mode.

Confirmed

Send main Reset to the DUT. This places the DDS to a known state.

Confirmed - See SPI Trace

Program the registers to the desired configuration.

Confirmed - See SPI Trace

I'm still seeing the same behavior. Any other ideas?
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ssmith
on Nov 22, 2022 2:17 PM in reply to Jules.Nikko
0
Hi Jules.Nikko ,

From the listed guide, here are the things I have checked.

This is the set-up in which the evaluation board is 100% to be controlled externally. The basic things to be checked are the following:

Most of the DDS evaluation boards have logic buffers between the USB interface and the DDS. There are jumpers that enable/disable these logic buffers. Locate for these jumpers and set to disable to tri-state the ICs on the evaluation board. The user may refer to the evaluation board schematic to easily identify these jumpers.

I'm not using an eval board.

Connect ALL the required input pins to the external circuitry via interface cable to control the DUT. Some critical inputs are the main_Reset and the external power down pins.

I'm controlling all input pins except for Loop Filter, which is not connected to anything. Sync_In is grounded.

Selecting the profile mode can be done two ways: hardwire each profile pin to logic 1 or 0, or connect interface cable from these pins to control it externally.

AD9951 doesn't have profile pins.

Set the Function Pins (applicable only to AD9914/AD9915) to the desired parallel-port configuration.

N/A for AD9951

Apply power, reference clock and control ALL digital inputs. When controlling the digital inputs, make sure that there is a defined logic state for each input. The external power down must be set to logic 0 to ensure the DDS is not in power-down mode.

Confirmed

Send main Reset to the DUT. This places the DDS to a known state.

Confirmed - See SPI Trace

Program the registers to the desired configuration.

Confirmed - See SPI Trace

I'm still seeing the same behavior. Any other ideas?
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Jules.Nikko

on Dec 2, 2022 1:19 AM in reply to ssmith
0
Hi ssmith ,

Apologies for the delay. I'm thinking this issue might be on the Raspberry Pico. However, I can't fully verify it due to limitations on my end. I will try to consult these with other experts and will come back here in case I have a solution, but this might take a while.

All the best,

Jules
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ssmith
on Dec 7, 2022 2:42 PM in reply to Jules.Nikko
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Thank you! As an update, I have gotten the chip outputting a function using a different controller (a Teensy) so at this point I've confirmed that the hardware is functional and that it is likely the Pico's fault. As I try to see what the differences are I will post an update for future reference.
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AD9951 Unresponsive to SPI communication.