Part Number: DAC124S085 Other Parts Discussed in Thread: AM625 Tool/software: Hi , I am using this DAC board DAC124S085EVM Evaluation board | TI.com and linux drivers from kernel.org/doc/Documentation/devicetree/bindings/iio/dac/ti%2Cdac082s085.yaml driver and below is my node , &main_spi0 { ti,spi-num-cs = ; status = "okay"; spidev@0 { compatible = "rohm,dh2228fv"; reg = ; spi-max-frequency = ; }; dac@1 { compatible = "ti,dac124s085"; reg = ; spi-max-frequency = ; spi-cpha; vref-supply = ; }; }; I have two slaves on my board and only DAC is connected. I am using AM625 SOM and I can see SPI transections as below over SPI lines using logic anaylser for 100 counts it sends below on each channel Channel VOA when I write 100 using echo 100 > /sys/bus/spi/devices/spi0.1/leds/dac124s085-0/brightness On SPI lines I see signals = 0x64 0x10 = 01100100 00010000 echo 100 > /sys/bus/spi/devices/spi0.1/leds/dac124s085-1/brightness On SPI lines I see signals = 0x64 0x50 = 01100100 01010000 echo 100 > /sys/bus/spi/devices/spi0.1/leds/dac124s085-2/brightness On SPI lines I see signals = 0x64 0x90 = 01100100 10010000 echo 100 > /sys/bus/spi/devices/spi0.1/leds/dac124s085-0/brightness On SPI lines I see signals = 0x64 0xD0 = 01100100 11010000 above signals are as expected. but on HW this is the behaviour , I dont see any correct relation between my setting and Pin state. Other channels are affected too even when I am not sending command to update all and values are incorrect see below table , I tested one channel at a time and noted the behaviour on other channels. Channel under test Calculated Values using formula from datahseet Actual Values on IC using multimeter Other Channel voltage when I make a count change on channel under test Comments Channel A Expected Count Expected Voltage Actual Voltage on pin Actual Count Caculated using formula B C D A 0 0 0.0283 28.3 A 100 0.1 1.0403 1040.3 1.0403 1.0403 1.04 A 500 0.5 0.2768 276.8 0.292 0.279 0.41 keep changing A 1000 1 2.069 2069 2.069 2.065 2.065 A 1500 1.5 2.2598 2259.8 2.2618 2.2577 3.092 A 2000 2 2.2598 2259.8 2.2618 2.2577 0.024 A 3000 3 -0.063 -63 -0.065 -0.068 -0.071 changing gowing more low and again stable A 4095 4.095 0.5 500 0.498 0.514 0.498 Keep on increaing slowly Channel B Expected Count Expected Voltage Actual Voltage Actual Count A C D B 0 0 0.0493 49.3 B 100 0.1 1.1076 1107.6 1.1051 1.1035 1.104 B 500 0.5 0.334 334 0.289 0.394 0.45 keep changing B 1000 1 2.1333 2133.3 2.1318 2.1295 2.128 B 1500 1.5 2.2618 2261.8 2.2599 2.2577 3.155 B 2000 2 2.2618 2261.8 2.2599 2.2577 0.088 B 3000 3 -0.063 -63 -0.065 -0.068 -0.071 changing gowing more low and again stable B 4095 4.095 0.499 499 0.488 0.512 0.498 Keep on increaing slowly Channel C Expected Count Expected Voltage Actual Voltage Actual Count A B D C 0 0 0.00363 3.63 C 100 0.1 1.1678 1167.8 1.1694 1.1719 1.168 C 500 0.5 0.44 440 0.372 0.412 0.477 C 1000 1 2.1939 2193.9 2.1962 2.1977 2.193 C 1500 1.5 2.2577 2257.7 2.2599 2.2618 3.21 C 2000 2 2.2577 2257.7 2.2599 2.2618 0.152 C 3000 3 -0.073 -73 -0.075 -0.073 -0.075 changing gowing more low and again stable C 4095 4.095 0.513 513 0.49 0.54 0.498 Keep on increaing slowly Channel D Expected Count Expected Voltage Actual Voltage Actual Count A B C D 0 0 0.002 2 D 100 0.1 1.2311 1231.1 1.2333 1.2356 1.231 D 500 0.5 0.322 322 0.336 0.42 0.32 D 1000 1 2.2569 2256.9 2.2598 2.2618 2.258 D 1500 1.5 3.2825 3282.5 2.2599 2.2618 2.258 D 2000 2 0.215 215 2.2599 2.2618 2.258 D 3000 3 -0.073 -73 -0.075 -0.073 -0.075 D 4095 4.095 0.513 513 0.49 0.54 0.498 Keep on increaing slowly I am not sure why other channels are affected and why voltage on pins are not in map with the counts I write? when the other channels are affected if I read the value as cat sys/bus/spi/devices/spi0.1/leds/dac124s085-1/brightness it doesnt change but the output changes when I change channel count. I VA =5V and ref voltage is 4.095 as. I connect pins of DAC EVM as below 5V = 5V external power supply with 1A current limit GND= Common ground SYNC = CS CLOCK = CLOCK DIN = MOSI Please help as I do need stable output and single channel control. This is an urgent request please look into this matte r. Regards, Varsha
↧