acam PICOSTRAIN PS09-EVA-KIT User manual
Manual
PSØ9-EVA-KIT
19th May 2011
Document-No.: DB_PSØ9-EVA_en V0.1
Evaluation System for PSØ9
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PSØ9-EVA
Disclaimer / Notes
„Preliminary“ product information describes a product which is not in full production so that full information about
the product is not available yet. Therefore, acam messelectronic GmbH („acam“) reserves the right to modify this
product without notice. The information provided by this data sheet is believed to be accurate and reliable. However,
no responsibility is assumed by acam for its use, nor for any infringements of patents or other rights of third parties
that may result from its use. The information is subject to change without notice and is provided „as is“ without war-
ranty of any kind (expressed or implied). Picostrain is a registered trademark of acam. All other brand and product
names in this document are trademarks or service marks of their respective owners.
Support
For a complete listing of Direct Sales, Distributor and Sales Representative contacts, visit the acam web site at:
http://www.acam.de/company/distributors or refer to chapter 8 in this datasheet
For technical support you can contact the acam support team in the headquarter in Germany or the Distributor in
your country. The contact details of acam in Germany are:
Published by acam-messelectronic gmbh
©acam-messelectronic gmbh 2011
Table of Contents
PSØ9-EVA
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1 Introduction
2 Connecting Strain Gauges
1-1
2-2
2.1 HR - High Resolution Module
2.2 LC – Low Cost module
2.3 Connecting the Modules ...
Page
2-2
2-3
5.2 Running the Evaluation ...
5 Evaluation Software 5.1 Installing the PSØ9-EVA ... 5-2
5-3
8 Appendix
8-28.1 Schematic Diagrams
8.2 Layout PSØ9-EVA-HR Module
8.3 Layout PSØ9-EVA-LC Module
8-7
8-8
7.2 Document History
7 Miscellaneous 7.1 Literature Guide 7-2
7-2
6.2 Running the Assembler
6 Assembler Software 6.1 Installing the Assembler 6-2
6-2
4.2 Wiring diagram
4 Load cell 4.1 Technical Specification 4-1
4-1
3 Motherboard 3-1
3.1 LCD
3.2 External LCD driver 3-1
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acam ®, 1 ® are registered trademarks of acam-messelectronic gmbh
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PSØ9-EVA
1 Introduction
1.1 General
The PSØ9-EVA-KIT evaluation system provides a complete weighing system made of a main board with LCD panel,
two plug-in modules, a 10kg load cell platform and Windows-based evaluation and assembler software. Optionally,
the TTL-232R-3V3 cable, a USB TTL serial cable from FTDI is provided if the UART in the PSØ9 is to be tested. The
EVA-Kit offers extensive and user-friendly configuration and evaluation of the PSØ9 single-chip solution for weigh
scales.
1.2 System Overview
PSØ9-EVAL-MB Main Board
LCD display 22 x 51mm²
Interface to external LCD controller, Holtek HT1620
Power select by 2 jumpers:
Battery holder for CR2032
Wall power supply, Voltage selectable by on-board
jumpers
9 Push buttons (resistive keys)
4 Capacitive (touch) keys
A SPDT switch to select either SPI or IIC serial inter-
face between the PSØ9 and the PICOPROG program-
mer
UART interface
PSØ9-EVAL HR-Module
For up to 100,000 stable scale divisions & solar
applications
Up to 4 half bridges / Full bridge / Wheatstone
bridge
4 layer PCB
PSØ9-EVAL LC-Module
For up to 30,000 stable scale divisions and low cost
applications
Up to 4 half bridges / full bridge / Wheatstone
bridge
2 layer PCB
PICOPROG V2.0 Programmer
(USB to SPI/IIC interface)
10kg Load Cell
350 Ohm sensor
Mounted on platform
Wired as 2 half bridges with 1 span compensation
resistor
Optional FTDI TTL-232R-3V3 cable (available upon
request). This cable can be provided to test the UART
of the PSØ9 by establishing communication between
the UART of PSØ9 and a serial terminal application on a
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Windows PC.
1.3 Component List
PSØ9-EVA-MB Motherboard
PSØ9-EVA-Module-HR Plug-in module- High resolution
PSØ9-EVA-Module-LC Plug-in module- Low cost
PICOPROG V2.0 Programmer
Demo scale 10kg load cell with platform
High density DSUB15 cable Connecting the Evaluation board to the programmer
USB cable Connecting PICOPROG to the PC
Wall power supply
CD-ROM Incl. software and data sheets
Optional - FTDI TTL-232R-3V3 cable (upon request)
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2 Connecting Strain Gauges ......................................... 2-2
2.1 HR - High Resolution Module ................................................................................2-2
2.2 LC – Low Cost module .........................................................................................2-2
2.3 Connecting the Modules (HR and LC) ....................................................................2-3
2.3.1 Capacitor Selection and Assembly.................................................................2-3
2.3.2 Half bridge .................................................................................................2-3
2.3.3 Half bridge connection for Solar Applications .................................................2-4
2.3.4 Full bridge ..................................................................................................2-5
2.3.5 Wheatstone Full Bridge ...............................................................................2-7
2.3.6 Quattro mode .............................................................................................2-8
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2 Connecting Strain Gauges
The evaluation system comes with the load cell already connected to the plug-in module.
In the following we will explain how a user can apply his own load cell. In case of sensors with other than 350 Ohm
resistance the discharge capacitor Cload has to be adapted.
The 2 different plug-in modules are designed to support various applications of PSØ9. For high resolution and solar
applications, for up to 100,000 stable scale divisions, the external bipolar comparator circuit is used. For applica-
tions with lower current consumption and low resolution requirement, the LC variant is used, running with the inter-
nal comparator. The LC module has minimum components and is the ‘low-cost’ variant therefore; however resolution
will be clearly lesser than with the HR module.
2.1 HR - High Resolution Module
The HR module is targeted for high resolution and solar applications, for up to 100,000 stable scale divisions. The
external bipolar comparator circuit is used in this module.
It is possible to measure up to 4 half bridges. Due to the PICOSTRAIN measurement principle the system does not
need a full bridge. Two resistors, in the following called half bridge, are sufficient.
Figure 2-1: High Resolution Module
2.2 LC – Low Cost module
This is a low-cost version of the High resolution module, with minimum necessary components for operation. The
following are the distinct features that differentiate the LC module from the HR module:
1. No external comparator. This makes the LC module suitable for applications with high, but not the highest
resolution. The internal comparator is used. This reduces the base resolution by 0.8 bit compared to the external
comparator.
2. The 4 MHz ceramic crystal oscillator is not present and there is no possibility to connect an external RC
oscillator to PSØ9. Thus the PSØ9 can be operated only with the built in RC-oscillator. Operating the PSØ9 with the
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PSØ9-EVA
internal RC oscillator is known to limit the resolution to approximately 16 bits. An advantage is the lower current
consumption, which is around 1.2 mA current at 3V for maximum performance. To configure the internal oscillator
for operation please refer to section 4.1 of PSØ9 data sheet.
Figure 2-2: Low-cost Module
2.3 Connecting the Modules (HR and LC)
2.3.1 Capacitor Selection and Assembly
The PICOSTRAIN measurement principle is based on measuring the discharge time of a capacitor. For this reason
the correct size and material of the capacitors is significant to achieve best measuring results. In general we recom-
mend a discharging time in the range of
τ= 0.7*R*C = 80 to 120 µs.
As material we recommend C0G or CFCAP (Multilayer ceramic from Taiyo-Yuden). X7R capacitors can be used, too,
but will show some minor loss in temperature stability.
The recommend values are:
Rsg = 350 Ohm Cload = 300 nF to 400 nF
Rsg = 1000 Ohm Cload = 100 nF to 150 nF
The plug-in module is pre-assembled with Cload = 4 x 100 nF = 400 nF.
2.3.2 Half bridge
A half bridge is sufficient to run the PSØ9 evaluation system. The following picture shows how to connect the half
bridge the conventional way. It is basically connected to the pads A and B (SG_A1 and SG_A2, SG_B1 and SG_B2
are shorted). For the gain and temperature measurement, external resistors Rext1 and Rext2 are connected the
pads C and D (also shorted).
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Value of Rext1 = Rext2 = Rsg, the strain gage resistance. For e.g. with respect to Figure 2-3a, for a load cell with
Rsg = 350 Ohm and Rspan=45 Ohm, Rext1=Rext2= 350+45 = 395 Ohm
Figure 2-3a: Half Bridge, Classical
An alternative way of connecting a half bridge to PSØ9 is shown below, where the unused ports C and D are connec-
ted parallel to Ports A and B respectively. The external resistors are avoided in this connection. The option for using
an external comparator is available only on the HR-module.
Figure 2-3b: Half Bridge, Alternative
Please note: Both wiring options shown in figure 3a and 3b have to be done externally, i.e. at the solder pad of the
module. There are no wiring or placement options on the module itself.
2.3.3 Half bridge connection for Solar Applications
In solar applications the reduction of the current consumption has the highest priority. The unique capability of
PICOSTRAIN allows us to modify a full bridge load cell in such a way that it becomes a half bridge with twice the resis-
tance. So with 1 kOhm strain gauges the load cell shows a total resistance of 2 kOhm. The current into the sensor is
reduced by a factor of 2. This option is reasonable in case all the strain gauges are on one side of the load cell.
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Figure 2-4: Half Bridge, Solar
2.3.4 Full bridge
For PICOSTRAIN a full bridge is ideally separated into two half bridges. This wiring can increase the resolution com-
pared to Wheatstone bridges by 0.6 bit.
Figure 2-5: Full Bridge
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Existing sensors with Wheatstone bridge connection might be adapted just by changing the wiring according to the
following picture.
Figure 2-6: Adapted Load Cell Wiring
For certain advantages like resolution, PSRR etc. depending on the application, it might be necessary to use the
PSØ81 compatible mode of PSØ9. For details on this mode and its associated advantages, please refer to section
3.3.5 of PSØ9 data sheet.
Figure 2-7: PSØ81-compatible wiring
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2.3.5 Wheatstone Full Bridge
Existing load cells in Wheatstone configuration can be connected to the module without any modification as long as
they have only one or no compensation resistor. In case the bridge has two compensation resistors one of those
needs to be shortened.
In general Wheastone wiring will end in 0.6 bit less resolution compared to PICOSTRAIN wiring. It might be reaso-
nable to use Wheatstone bridges in case of cables to the sensor longer than 0.5 m. The following figure shows the
connection of the Wheatstone bridge.
Figure 2-8: Wheatstone Bridge
The PICOSTRAIN measurement principle is based on measuring the discharge time of a capacitor. For this reason
the correct size and material of the capacitors is significant to achieve best measuring results. For Wheatstone,
the discharging time is furthermore reduced by the factor of 0.7, The following formula can be used to calculate the
discharging capacitance.
τ= 0.7*0.75*R*C = 60 to 110 µs.
As material we recommend C0G or CFCAP (Multilayer ceramic from Taiyo-Yuden), X7R capacitors can be used, too,
but will show some minor loss in temperature stability.
The recommend values for Wheatstone mode are:
Rsg = 350 Ohm Cload = 300 nF to 400 nF
Rsg = 1000 Ohm Cload = 100 nF to 200 nF
Please note: In Wheatstone mode the operation via SPI interface is recommended. If IIC is to be used, please opera-
te in Single Conversion Mode. See also the bug report in the PS09 data sheet.
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2.3.6 Quattro mode
In quattro mode the PSØ9 measures 4 half bridges. The 4 half bridges are measured independently and the gain of
each half bridge can be corrected separately. Typical applications are bathroom-scales, baby or platform scales.
Figure 2-9: Connecting four half bridges or two full bridges in One sense mode
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PSØ9-EVA
3 Motherboard
The motherboard connects to the PICOPROG programmer. It serves the various power options. It holds the LCD
panel. The 9 push buttons (resistive keys) and 4 capacitive keys can be used in stand-alone operation.
The jumpers for power select can also be used to measure the current consumption of the system.
3.1 LCD
The LCD has the following specification:
Duty ¼, Bias 1/3, Operating voltage 2.5V, Operating temperature 0°C to 50°C.
Figure 3-1: Motherboard
3.2 External LCD driver
PSØ9 offers the possibility to support an external LCD driver. Therefore a simplified SPI master mode is program-
med in the PSØ9, especially adapted to Holtek HT1620 LCD driver. Three GPIOs of the PSØ9 are used to realize the
SPI master interface to connect to the Holtek driver. The PSØ9 can generate a configurable 32 kHz clock needed to
drive the HT1620 driver, thus avoiding the necessity of an external crystal oscillator for the LCD Driver. One GPIO is
additionally used to for this clock.
The LCD driver on the PSØ9 Motherboard can be powered by the output of a voltage regulator (fixed voltage of 3V).
Optionally the LCD driver can be powered by the voltage selected by the on-board jumpers on the motherboard (vol-
tage adjustable). The appropriate jumper (J26 (fixed) or J27 (adjustable)) has to be soldered in order to select the
source of the LCD’s power supply.
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Figure 3-2: External LCD Driver
The following picture shows the connection of an external LCD driver circuit:
Figure 3-3: External LCD Driver Wiring
A flowchart showing the general sequence to program the PSØ9 in order to operate the external LCD driver is illus-
trated in Section 4.8 of the PSØ9 Data sheet. The flowchart is however based on the idea that GPIOs 5, 6, 7 would
be used as the SPI communication lines. The PSØ9 EVA board supports communication to the Holtek driver only
via GPIOs 0, 1, 2. Sample programs which use the LCD for display, along with the appropriate header files that are
specific to the Holtek driver, HT1620 are available as part of the PSØ9 Assembler examples.
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4 Load cell
The evaluation system is shipped with a ready made demonstration scale connected to the high resolution module.
The load cell is model CZL601SE-10kg from Hua Lan Hai (http://www.chinesesensor.com/Single-point_Load_Cell.
html).
4.1 Technical Specification
Table 4-1: Technical Spelcification
Maximum load kg 10
Comprehensive error C2 %F.S. 0.02
Rated output mV/V typ. 1.85
Non-linearity %F.S. 0.03
Hysteresis %F.S. 0.03
Repeatability %F.S. 0.02
Creep %F.S./30min. 0.02
Resistance Ohm 350 ±5
Compensation resistor Ohm 42 ±5
Compensated temperature range °C -10 to +40
Operating temperature range °C -35 to +65
Safe overload %F.S. 120
Ultimate overload %F.S. 150
Mechanical dimensions:
Base plate 200 mm x 100 mm
Weighing plate 90 mm x 90 mm
Total height
70 mm
4.2 Wiring diagram
Figure 4-2: Wiring diagram (to be verified)
To be verified
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PSØ9-EVA
5 Evaluation Software.................................................. 5-2
5.1 Installing the PSØ9-EVA Software ........................................................................5-2
5.2 Running the Evaluation Software..........................................................................5-3
5.2.1 Setup Page ................................................................................................5-3
5.2.2 Measurement Page .....................................................................................5-4
5.2.3 Graphic Page ..............................................................................................5-5
5.2.4 Front-End Page ...........................................................................................5-6
5.2.5 ALU Page ...................................................................................................5-7
5.2.6 Expert Page ..............................................................................................5-8
5.2.7 Memory Page ............................................................................................5-9
5.2.8 Interfaces Page .......................................................................................5-10
5.2.9 Temperature Compensation Page................................................................5-11
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5 Evaluation Software
5.1 Installing the PSØ9-EVA Software
The PSØ9-EVA software runs under the following operating systems
Windows 2000
Windows XP
Windows Vista (please use the software/drivers for Windows 7)
Windows 7
Please follow the described procedure to install the software and driver:
NOTE: Ensure that the Picoprog V2.0 programmer is disconnected before starting the procedure.
1. Install the device drivers by running setup.exe from Driver/PicoProg v2 Driver Installer Stand-Alone. Select the
shown default paths and continue the setup procedure.
2. At the end of step 1, you will be asked in a separate window (batch-file) to connect the Picoprog V2.0 program-
mer. Please insert the PicoProg to your computer.
3. The driver is installed; a windows message may pop up asking you to install the driver though it is not signed.
Please install it anyway.
4. The batch file asks you to plug in the programmer and it is now enumerated. Unplug and insert the Picoprog
programmer.
5. Install the PSØ9 Assembler software from Software\PSØ9-Assembler-Software\XP-WIN7\Volume2-0-xx\se-
tup.exe from the CD.
6. If required perform a system restart.
7. The assembler software is now ready to use. Open the PSØ9 Assembler software, the respective firmware is
downloaded into the programmer automatically and the LED on the Picoprog programmer is illuminated.
8. You can test to find the programmer on the ‘Download’ page and press ‘Get Device Info’.
9. Install the evaluation software now from Software\PSØ9-Evaluation-Software\Setup.exe
10. Once the software is installed, launch the application from the start menu. The software opens and a pop up
window asks to select a firmware for Picoprog.
11. Select the hex-file (firmware) for Picoprog in the folder “data” The hex-file itself is named PSØ9_FWxx.hex
12. If everything is correctly installed, the USB identifier must be USB:: 0x194E:: 0x100F::NI-VISA.
13. Please confirm connection by clicking the button ‘Verify Interface’. ‘OK’ should be shown in the pop-up window.
Optionally you can see a video-tutorial about the PS08 Assembler Software (which structurally the same as the
PSØ9 Assembler) by watching the video from:
ASM-Screencast.exe in PS08-Assembler-Introduction\Flash folder.
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