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Part Number: PGA900EVM
I am using PGA900EMV development board and Code Composer Studio v6. I have built project, connected to target (I am using XDS200), run->load ->load program. Compiler gives me message: PGA900 OnFileLoaded is done. I assume that PGA900.out file and program was loaded to micro(TI example code).
a) Problem I have is I can't change output voltage. For example if I am changing DAC gain value register, I can see what register values are changing too, but Vout value is not changing ( I am measuring Vout on TP1 wrt TP39). Why Vout is not changing? What I am doing wrong?
b) Also I have connected USB2ANY and PGA900 GUI. In microcontroller mode tried to change bridge value - no changes in Vout value. Why Vout is not changing? What I am doing wrong?
c) In digital mode tried to change bridge value (configured ADC, DAC) - no changes in Vout value. Why Vout is not changing? What I am doing wrong?
Precision ADC Applications
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In reply to Scott Cummins:
Please find below my questions/comments below highlighted in blue.
Please try loading the hex file generated from your project to the PGA900 through the DEVRAM for testing and see if it will work that way.
Tried to load hex file to DEVRAM - not wotking. Max value I can get 5.03V (DAC REG0=3FFF) and minimum value I can get is 4.324V (does not matter what I am writing to DAC_REG0).
Gain =4V, DAC_ENABLED, TEST_MUX_DAC_EN - enabled, DAC config= 1.25V.
Before that, however, can you please confirm that your EVM and PGA900 device are working properly by running the PGA900 without firmware? You can enable all of the analog blocks for the PADC and turn on the bridge excitation in the GUI then monitor the ADC in the ADC capture window.
Changed PGA900 chip to another chip (in case it was damaged). I have fallowed steps in PGA900 EVM Quick Start Guide. I can read ADC values in GUI - temperature and pressure values.
After setting the TEST_MUX_DAC_EN in the DAC configuration menu you can set the DAC DATA registers to any value and make sure that it is changing at the VOUT pin.
DAC Gain=4V. When I write to DAC REG0=3FFF,Vout=5.03V; DAC REG0=1FFF Vout=4.38V; DAC REG0=0 Vout=5.099V.
DAC Gain=10V. When I write to DAC REG0 any values, Vout=5.09V and it is not changing no matter what I am writting to DAC REG0. PSU for EVM is 15V.
Vout is changing only when I am changing gain. Vout is measured on TP30 wrt TP39.
Finally, since you are measuring the voltage at VOUT I will assume you are using the voltage output mode. Are the jumpers set properly for voltage output mode according to the user's guide?
I have not changed jumpers position. Jumpers are configured in default mode (voltage mode) as per PGAxxxEVM-034 Users Guide Table1. J14 pins 2 and 3 are closed if pins 1 &2 are closed Vout starts to oscillate.
Do you understand why is it not working for me even if I am fallowing TI User Guides? What I am doing wrong? Any ideas?
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