Menu
▾
▴
Tree [871b21] master v0.35 / History
Paul Pham
Read Me
AD9910 dds synthesizer firmware documentation ============================================= Overview -------- This is the documentation for the synthesizer board which is meant to work with programmable pulse generator as designed by Paul Pham link:[http://pulse-programmer.org] The features of the board are: - Onboard Cyclone II FPGA for increased flexibility - AD9910 DDS with 14Bit DAC and 1Gs/s clock - AD9744 DAC and AD8367 VGA for pulse shaping - 32Bit LVDS bus for high speed data transfer This documentation is focused on the programming of the FPGA. This is accomplished in the VHDL hardware description language. This board is only supported by the sequencer2 python compiler/server. The original vhdl-ad9910 source code was written by Philipp Schindler at Innsbruck. Additional modifications were added by Paul Pham to sample data multiple times before latching out stable data to overcome bus sample errors at UW Seattle. There is only one backward-incompatible change to Philipp's version, which is that DDS register addresses now come first in the datastream, before the register data. This requires the changes in the ppham branch of the sequencer2 Python compiler in Mercurial. The source code is spread over following files: `------------------------`--------------------------- Filename Function ----------------------------------------------------- dds_controller.vhd top entity, opcode decoding dds_serial_decoder.vhd decoding and container for dds_serial_fifo dds_serial_fifo.vhd wrapper for fifo buffer and dds_serial_bus. dds_serial_bus.vhd low-level serial port operations for AD9910 dds_stabilizer.vhd low-level data sampling to latch out stable levels. ddslib.vhd configuration, opcode definition phase_register.vhd phase registers ----------------------------------------------------- The VHDL files can be compiled with the free quartus II web edition which is available at link:[http://www.altera.com/] Compilation ~~~~~~~~~~~ To compile the firmware open the dds_controller.qpf file in quartus II and press ctrl - L To program the firmware on the FPGA open the Programmer in quartus II and select active-serial-programming. Add the file dds_controller.pof for programming and press start. Bus definition ~~~~~~~~~~~~~~ The control bits in the instruction word are: `---------------------------------------`-------------------------- Function Bus bits used ------------------------------------------------------------------- opcode (31:27) data available (26) address (not implemented) (25:22) phase register wren / DRCTL (21) phase register set current /DHOLD (20) phase register address (16:19) dds_drctl (16) dds_drhold (17) dds_ramp_config (18) data bus (15:0) -------------------------------------------------------------------- Write process timing: ~~~~~~~~~~~~~~~~~~~~~ A write process on the LVDS bus is specified with 3 clock cycles of the PCP-FPGA. The length of one cycle is 10ns. - Set the data bus , bits(15:0) - Set opcode, dds address and other bits except data available bit(25) - Set data available bit(25) The data available bit should be unset after one clock cycle. This is a conservative and hopefully save method to write data to the bus. DDS interface ~~~~~~~~~~~~~ The ad9910 dds has internal registers which determine the mode of operation. These registers have to be programmed over a serial SPI interface. To speed up the data transfer from the PCP to the DDS the data is transmitted over the parallel board to the FPGA on the DDS board. This data is then written into the DDS via the serial interface. Each configuration register has to be programmed at once. As the registers are up to 64Bits wide the data from the PCP is stored in a FIFO implemented the FPGA on the DDS board. A write cycle to the DDS is accomplished as follows: - The data is split in 16bit words - This words are transmitted from the PCP to the FPGA - The 8 bit address word of the register is transmitted - The FIFO is read until it is empty Testing the board: ------------------ Connecting the board ~~~~~~~~~~~~~~~~~~~~ - Connect 5V to the analog and digital power supply - Connect 10V..12V to the analog 10V suply. - Connect 100MHz to the T_DDS_FPGA connector - Connect 800MHz to the connector P1 - Set the jumpers as shown in the image INSERT IMAGE OF BOARD HERE To test the functionality of the DDS board following procedure is recommended. Test the Voltage regulators ~~~~~~~~~~~~~~~~~~~~~~~~~~~ - Connect a single board to a power supply with an adjustable current limit. - Set the current limit to about 10mA and the Voltage to 6V - Turn up the curent limit. If the board draws more than 400mA there is most likely a short circuit on the board. - Check the desired output voltage with an oscilloscope/multimeter INSERT VOLTAGES AND IC NUMBERS HERE Test the LVDS Bus ~~~~~~~~~~~~~~~~~ To test the functionality of the LVDS Bus a working sequencer-rev.C board and a suitable breakout board is needed. Furthermore a JTAG download cable and a quartusII installation is necessary - Activate the test_lvds_bus.stp SignalTap file in quartusII - Compile the VHDL source with quartusII - Connect the JTAG cable to the JTAG board (J2) - Program the FPGA (with JTAG, NOT active serial programming) - Start ipython in the sequencer directory and execute following code: ------------------------------------- from tests.test_hardware import * t1 = HardwareTests(nonet=True) t1.test_lvds_bus() ------------------------------------- - Ensure that the bus values are correct. INSERT SCREENSHOT Another quick (but incomplete) test of the LVDS Bus can be performed by generating DAC events with the sequencer and checking the output voltage of the DAC. Test the DDS ~~~~~~~~~~~~ - Start ipython in the sequencer directory and execute following code: ------------------------------------- from tests.test_hardware import * t1 = HardwareTests(nonet=True) t1.test_dds_simple() ------------------------------------- - Test the output of the DDS. INSERT DATA HERE If these tests were succesfully you most probably have a working system. Test phase coherent switching ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - Use a fixed frequency source as reference - Switch the DDS board to the same frequency with different phases. - Check the pghase relation of the two signals with an RF-mixer Programming guide ------------------- Writing a register on the dds ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ - Split the data in 16bit words - Write the data subsequentially into the FIFO with the fifo write insn - Set the upper 8 bits of the data bus to the desired address - Provide the dds address Opcode and the address data until the register is set Load the phase register ~~~~~~~~~~~~~~~~~~~~~~~ - Split the frequency tuning word into two 16Bit words - Write the lower word with wren=0 and set current=0 and the load phase opcode - Write the upper word with wren=0 and set current=1 and the load phase opcode - Set the phase register address bits - Write load_wren_opcode and set_current=1 do not change data on pins 0:15 Phase coherent switching ~~~~~~~~~~~~~~~~~~~~~~~~ This is not properly implemented yet - Set the dds frequency either by writing the register or the profile - Provide the pulse phase opcode - Wait 4 cycles - Provide the dds update opcode Set the DAC ~~~~~~~~~~~ - Set the data bus bits (13:0) - Provide the dac amplitude opcode Ramp Control ~~~~~~~~~~~~ Set the registers over the serial port. Control then the drhold and drhold pins of the DDS. Preliminary Opcode specification -------------------------------- Already implemented opcodes ~~~~~~~~~~~~~~~~~~~~~~~~~~~ `--------------`---------`----------------------------------- Name Opcode Function ------------------------------------------------------------- nop 0x0 Do nothing dds_addr 0x1 Write content of FIFO to given DDS fifo_wr 0x2 Write lower 16bits to FIFO dds_profile 0x3 Set the DDS profile bits dac_amplitude 0x7 Set the DAC for the VGA load_phase 0xa Load the phase register pulse_phase 0xb Write given phase register to DDS fifo_reset 0x1f Clear the FIFO dds_update 0x4 Update the DDS or control ramp generator ------------------------------------------------------------- Proposed opcodes ~~~~~~~~~~~~~~~~ `------------`------------------------------- Name Function --------------------------------------------- dds_sweep Start/Stop a DDS sweep dds_ramp Generate a DDS amplitude ramp all_reset Reset the FIFO and the DDS --------------------------------------------- License ------- (c) 2008 Philipp Schindler. This work is published under the GNU Public License The file phase_register.vhd is copyright by Paul Pham and released under the BSD License.
