Okotech DAC-40-USB User manual

OKO Tech DAC40 USB 1
DAC unit «DAC-40-USB»
Manual
1. Purpose
Digital-to-analog converter unit «DAC-40-USB» is intended to provide
multi-channel voltage output. It is controlled from a personal computer via a USB
port. Its primary purpose is to drive deformable mirrors produced by OKO
Technologies.
2. Specifications
V 1.0 V 2.0
Analog outputs 40 40
Output range 0 – 5.5 V 0 – 5.0 V
Output resolution 12 bits (4096 levels)
Range of adjustment of the maximum
output voltage
2.5 – 5.5 V 2.6 – 5.0 V
Ohmic load, each channel ≥100 kΩ≥100 kΩ
Load capacitance, each channel ≤500 pF ≤500 pF
Synchronous output for all channels.
Power is provided via the USB port.
3. General design
«DAC-40-USB» is designed as a PCB with two double-row angle
connectors BH-20R (male) and a B-type USB connector; it is mounted in a
compact housing. Pins of the output connectors are labeled according to the

OKO Tech DAC40 USB 2
numbering order of the output channels. The maximum output voltage value can be
adjusted (all channels simultaneously) by a variable resistor, whose slot is sunk in
a hole on the front side of the unit (Fig. 2).
To provide access to the PCB (Fig.1, 2) one should disconnect upper and
lower decks of the housing by simultaneous depression of their side surfaces. To
close the housing, the decks must be pushed vertically one to another till latched.
Fig. 1. «DAC-40-USB» view from the output connectors’ side
Fig. 2. «DAC-40-USB» view from the USB connector side
3.1. Jumper settings for version 1.0
Fig. 3. PCB layout and numbering of jumpers’ contacts for V.1.0
R
1
2
3
1
2
3
JP2 JP3
X3 X4

OKO Tech DAC40 USB 3
Jumpers JP2 and JP3 are mounted on the PCB (Fig. 3). By connecting
contacts 2 and 3 of jumpers JP2 and JP3 pin #1 of connector X3 (channel 1) and/or
pin #1 of X4 (channel 21), correspondingly, can be connected to the ground (see
Table 1). It should be kept in mind that when pin #1 of X3 (pin #1 of X4) is
connected to the ground, the 1st (or 21st, correspondingly) channel of the DAC is
disconnected from the connector.
Table 1
Jumper settings and output connectors commutation
JP2 Pin 1 of X3 JP3 Pin 1 of X4
1–2 Channel #1 output 1–2 Channel #21 output
2–3 Ground 2–3 Ground
3.2. Jumper settings for version 2.0
Fig. 4. PCB layout and numbering of jumpers’ contacts for V.2.0
Jumpers X3 and X4 are mounted on the PCB (Fig. 4). By connecting
contacts 2 and 3 of jumpers X3 and X4 pin #1 of connector X5 (channel 1) and/or
pin #1 of X6 (channel 21), correspondingly, can be connected to the ground (see
Table 2). It should be kept in mind that when pin #1 of X3 (pin #1 of X4) is
connected to the ground, the 1st (or 21st, correspondingly) channel of the DAC is
disconnected from the connector.
Jumpers X7 and X8 allow swapping pins 1 and 2 of the output connectors
X5 and X6 (see Table 2 for details).
Jumper X9 can be set to connect the outer case of the USB connector X2 to
ground.
direct
cross
1 2 3
X3
X
7
direct
cross X4 1 2 3
X8
X5 X6
X9
X2

OKO Tech DAC40 USB 4
Table 2
Jumper settings and output connectors commutation
4. Getting started
Before using the unit, it is necessary to check settings of jumpers or
appropriately configure those according to specifications of connected device(s) as
described above.
To put the unit into operation following steps must be done.
•Plug connecting cables into the output connectors of the unit.
•Connect the unit to the USB port of your PC using the USB cable. The
LED lit on the USB port face in 2-2.5 seconds indicates normal
operation of the unit.
•Install FDTI Direct Driver for Windows 98/2000/ME/XP from the
folder /Drivers of the supplied software CD. Updated drivers can be
downloaded from www.ftdichip.com. For version 2.0 you have to use
the driver version 2.00.00 or higher.
•Run TEST_DAC40.EXE, move the pointer of the output voltage into
Umax position, then adjust the output voltage to the required value by
rotation of the spindle of the variable resistor R. The level of the
output voltage must be measured by a voltmeter connected to one of
the output pins with respect to the grounded pin.
5. The program interface
5.1. General
Data transfer between PC and DAC via USB bus is managed by the interface
chip from FT245 series. To provide necessary speed of data transfer between PC
and DAC it is necessary to use FDTI Direct Driver. The corresponding program
interface is implemented in the library FTD2XX.DLL.
5.2. Application of the library FTD2XX.DLL
To provide access to the DAC, the following functions of FTD2XX.DLL
are implemented:
X3 X7 Pin 1 of X5 Pin 2 of X5 X4 X8 Pin 1 of X6 Pin 2 of X6
1–2 Ch #1 output Ch #2 output 1–2 Ch #21 output Ch #22 output
2–3 direct Ground Ch #2 output 2–3
direct Ground Ch #22 output
1–2 Ch #2 output Ch #1 output 1–2 Ch #22 output Ch #21 output
2–3 cross Ch #2 output Ground 2–3 cross Ch #22 output Ground

OKO Tech DAC40 USB 5
•FT_ListDevices – allows to detect the number of connected devices,
their serial numbers and specifications;
•FT_Open – opens of the device for data transfer;
•FT_Write – send a packet of control data from the PC to the device;
•FT_Close – closes the device.
Specifications of these functions are given in the programmer’s manual of the
library FTD2XX (file D2XXPG33.pdf in the folder /Driver of the software CD).
Examples of their use are given in Section 5.4.
5.3. Data interchange via USB
Control of the unit from an external program is organized by sending data
packets to the module. The data packet has 129 bytes size. An example of forming
of the data packet from an array of 16-bit values corresponding to output voltages
of the DAC unit is given in Appendix 1, function MakePacket.
When the data package is received and control words loaded into DAC
chips, synchronous setting of signal levels at the outputs takes place, and the
micro-controller enters the standby mode, waiting for the next data package. In this
mode, zero bytes transferred into the module via the USB bus are ignored. In order
to put the unit into the standby mode, it is necessary to fulfill transfer of data
package consisting of 128 zero bytes. It is recommended to perform this operation
when initializing the unit’s control cycles.
5.4. MakePacket function usage
To facilitate programming of the unit, one may use the function
MakePacket. It transforms an array consisting of 40 two-byte words, each of them
coding an output voltage at the corresponding channel, into the data packet, which
can be transferred via USB. Text of the function and an example of its usage are
given in Appendix 1.
When connecting two or more DACs «DAC-40-USB» to the computer it is
necessary to define their system numbers by means of FT_ListDevices function. A
detailed description of this function is given in file D2XXPG33.pdf, folder
/Driver in the software CD. An example of usage of function FT_ListDevices is
given in Appendix 2.
For synchronous control of the units one may use the function MakePacket.
It is implied that before this all devices «DAC-40-USB» are opened by means of
the function FT_Open, with preliminary defined system numbers of these
modules.

OKO Tech DAC40 USB 6
7. Calibration of the unit
Using the DAC unit it is necessary to keep in mind that the minimum
voltage generated by any output channel corresponds, in general case, to non-zero
control code. It is due to specifics of operation of the DAC chip. User can set the
minimum value of this parameter for each channel by adjustment of the maximum
output voltage max
U. To do this, run TEST_DAC40.EXE in «Custom» mode and
connect a digital voltmeter with accuracy not worse than 0.5 mV to the output of
the channel to be tested. Detect the minimum control code, whose unitary
increment changes the output voltage to approximately 4095/
max
U.
Appendix 1.
#include "ftd2xx.h"
void MakePacket(WORD *buf,BYTE *packet);// Function of data package for DAC formation
void dac_setup(void)
// Sample: To set voltages with level codes 0,100,200, … 4000
// at the DAC outputs 1,2,3, …, 40
{
WORD buf[40]; // Buffer of DAC channels
BYTE packet[130]; // DAC data package
FT_HANDLE DAC; // DAC descriptor
FT_STATUS fs = FT_Open(0,&DAC); // Open a device with system # 0(1,2,etc)
if(fs==FT_OK) // If the device is opened successfully
{
unsigned long BR;
for(int i=0;i<40;i++) // Fill up the buffer of channels with codes of
buf[i]=i*100; // voltage levels
MakePacket(buf,packet); // Transform buffer of the channels
// into data package
FT_Write(DAC,packet,130,&BR); // Transfer data package into the DAC
FT_Close(DAC); // Close the device
}
else {// Error handling … }
} // End dac_setup()
//---------------------------------------------------------------------------
static BYTE DAC_CHANEL_TABLE[40]= // Table of DAC channels
{
/*DAC-> 0 1 2 3 4 |
---------------------+ OUTPUT */

OKO Tech DAC40 USB 7
7, 15, 23, 31, 39, //| A
6, 14, 22, 30, 38, //| B
5, 13, 21, 29, 37, //| C
4, 12, 20, 28, 36, //| D
3, 11, 19, 27, 35, //| E
2, 10, 18, 26, 34, //| F
1, 9, 17, 25, 33, //| G
0, 8, 16, 24, 32 //| H
};
//---------------------------------------------------------------------------
void MakePacket(WORD *buf,BYTE *packet)
/* Form a data packet from the buffer of channels:
buf - an input array consisting of forty 16-digit words, which code
voltage levels of the outputs ##1-40
packet – the resulting 129-byte output array to be transferred into the unit via
USB bus
*/
{
BYTE *p=packet+1;
for(int i=0,s=0;i<8;i++,s+=5)
{
// Form address parts of control words for five DAC chips
*(p++)=0;
*(p++)=(i&4)?0x1f:0;
*(p++)=(i&2)?0x1f:0;
*(p++)=(i&1)?0x1f:0;
// form control codes from the array of voltages according to the table
for(int j=0,mask=0x800;j<12;j++,mask>>=1)
*(p++)=
((buf[DAC_CHANEL_TABLE[s+0]]&mask)?0x01:0) |
((buf[DAC_CHANEL_TABLE[s+1]]&mask)?0x02:0) |
((buf[DAC_CHANEL_TABLE[s+2]]&mask)?0x04:0) |
((buf[DAC_CHANEL_TABLE[s+3]]&mask)?0x08:0) |
((buf[DAC_CHANEL_TABLE[s+4]]&mask)?0x10:0) ;
}
packet[0] = 0xff; // non-zero starting byte
}
Appendix 2.
Sample code shows how to get the number of devices currently connected
FT_STATUS ftStatus;
DWORD numDevs;
ftStatus = FT_ListDevices(&numDevs,NULL,FT_LIST_NUMBER_ONLY);
if (ftStatus == FT_OK) {
// FT_ListDevices OK, number of devices connected is in numDevs
}
else {
// FT_ListDevices failed
}
This sample shows how to get the serial number of the first device found. Note that indexes are
zero-based. If more than one device is connected, incrementing devIndex will get the serial
number of each connected device in turn.
FT_STATUS ftStatus;
DWORD devIndex = 0;
char Buffer[16];
ftStatus =
FT_ListDevices((PVOID)devIndex,Buffer,FT_LIST_BY_INDEX|FT_OPEN_BY_SERIAL_NUMBER);
if (FT_SUCCESS(ftStatus)) {

OKO Tech DAC40 USB 8
// FT_ListDevices OK, serial number is in Buffer
}
else {
// FT_ListDevices failed
}
This sample shows how to get the product descriptions of all the devices currently connected.
FT_STATUS ftStatus;
char *BufPtrs[3]; // pointer to array of 3 pointers
char Buffer1[64]; // buffer for the product description of first device found
char Buffer2[64]; // buffer for the product description of second device
DWORD numDevs; // initialize the array of pointers
BufPtrs[0] = Buffer1;
BufPtrs[1] = Buffer2;
BufPtrs[2] = NULL; // last entry should be NULL
ftStatus = FT_ListDevices(BufPtrs,&numDevs,FT_LIST_ALL|FT_OPEN_BY_DESCRIPTION);
if (FT_SUCCESS(ftStatus)) {
// FT_ListDevices OK, product descriptions are in Buffer1 and Buffer2, and
// numDevs contains the number of devices connected
}
else {
// FT_ListDevices failed
}

OKO Tech DAC40 USB 9
8. Using with 37-channel micromachined membrane deformable mirror
«DAC-40-USB» can be used to drive a 37-channed micromachined
membrane deformable mirror (MMDM) produced by OKO Technologies. Two
amplifier boards and four cables from OKO Technology are required for this
purpose. Assembling of the system is described below.
•Disconnect «DAC-40-USB» unit from your computer. In order to provide
ground to the mirror and connect it to the ground of the amplifier boards,
jumpers X3 and X4 of the unit should be set to the position 2-3. If the mirror
is supplied with a full set of control electronics, the jumpers should be
already properly configured.
•Connect the amplifier boards (or amplifier units) to «DAC-40-USB» unit
using 20 pins-to-26 pins cables, observing the order of numbering, e.g., the
amplifier board number 1 should be connected to X5 output connector,
whereas the board number 2 should be connected to X6 connector.
•Supply power to the amplifier boards (units) as specified in the mirror
manual.
•Connect «DAC-40-USB» to the computer using a USB cable. Turn on the
low voltage power supply, then the high voltage one.
•The folder /mmdm37ch_vc of the software CD contains simple command-
line utilities for control of the mirror, which are compiled with Visual C++
6.0. Enter this folder from the command line and type “am_set 4095”; it will
set the maximum voltage level at the output of the unit.
•Measuring the voltage between the ground pin (pin 20) and any control pin at
the output of any amplifier board, adjust it by turning the variable resistor R
until the maximum supply voltage for this mirror is achieved. If the mirror is
supplied with a full set of control electronics, the resistor Ris already
adjusted.
•Turn off the high voltage power supply. Connect the mirror to the amplifier
boards using 20 pins-to-20 pins cables, also observing the numbering. Fix the
cables to the optical table.
•Turn on the high voltage power supply. Now you can use the mirror.
The following utilities are provided to drive the mirror.
•“rotate” sets the maximum value (4095) to all channels of the mirror, one by
one.
•“am_set N” sets the same voltage Nto all actuators, where Nis in the range
0…4095.
•“19_set” sets 4095 to 20-37 channels of OKO 37ch mirror and 0 to other
channels.
•“set_channel N” sets 4095 to N-th channel and 0 to other channels.
•“smiley37” generate a smiley-like shape on the mirror.

OKO Tech DAC40 USB 10
If you need to recompile the utilities with Visual C++, copy the whole folder
/mmdm37ch_vc, enter it in the command line and type “nmake”.
9. Using with other deformable mirrors
The CD suipplied with «DAC-40-USB» also contains sample control programs for
other deformable mirrors from OKO Technologies. These programs include
“am_set”, “rotate” and “set_channel” utilities similar to those described in
Section 8. These are written in Visual C++ and accompanied by a make file for
recompilation. The samples can be found in the following directories.
mmdm79ch_40mm_vc - 79-channel 40 mm MMDM connected to two USB units;
mmdm_lin19ch_vc – 19-channel linear MMDM connected to one USB unit;
pdm109ch_50mm_vc - 109-channel 50 mm PDM connected to three USB units;
piezo19ch_vc – 19-channel 30 mm PDM connected to one USB unit;
piezo37ch_50mm_vc – 37-channel 50 mm PDM connected to one USB unit;
piezo37ch_2005_vc – 37-channel 30 mm PDM (design of 2005) connected to one
USB unit;
piezo37ch_vc – 37-channel 30 mm PDM (old design) connected to one USB unit;
piezo_lin20ch_vc – 20-channel liner PDM connected to one USB unit.
For hardware connections, please refer to the manual of the deformable mirror.