 Hello, and welcome to this presentation of ADC120 Evaluation Tools. My name is Gregory Gossignac, I'm application engineer at ST Microelectronics, and today I will guide you through this presentation. I will start with a quick presentation of ADC120, then we will see in details its evaluation board, and finally, I will show you a software demo using this board. So let's start with the device presentation. Here is the basic principle of an ADC. The purpose is to convert an analog signal from the real world into a digital signal, which can then be processed by software. Let's see the details of the ADC device from ST. ADC120 is a 12-bit analog-to-digital converter with 8 input channels and a sampling rate from 50k to 1 nega-sample per second. It has high precision for accurate measurements, so when we talk about precision for an ADC, the important parameters are the effective number of bits, which is 11.7 bits typical for ADC120, and also the INL and DINL parameters, 0.4 LSB typical. It has a simple digital connection by SPI, and it can be interfaced with various ST amplifiers, like TSX711, TSZ121, or TSU111. It provides flexibility thanks to the 8 analog channels and a sampling rate up to 1 nega-sample per second. And it has a poor consumption of 6.6 mW under a supply voltage of 3.3V. This is a robust device with an extended temperature range from minus 40 to 125°C, and it has 4 kV ESD protection. On this slide, you can see the block diagram just here. The device has two power supplies, one for the analog block, AVCC, and one for the digital block, DVCC. On the left, you can see the 8 inputs connected to a multiplexer, where you need to select which channel to measure. Then the signal goes through the 12-bit ADC converter, which is based on the successive approximation register, SAR, with internal track and hold cell. At the end, you have the logic control block, which is used to manage the SPI signals, serial clock, chip select, data in and data out. At the bottom, you can see the package for this device, which is TSSOP16. On the right-hand side, you have the pinout of this package, with below the description of all the pins. Now, let's take a look into the SPI interface. Here you can see the timing diagram for the digital signals. The first three signals here are sent from the SPI master interface, for example, from a microcontroller to the ADC device. And this device will answer back to the data out line, back to the microcontroller. The first signal is a chip select. You need to set the level to low to enable the ADC device. Otherwise, when the level is high, the device stays in power down mode. The second signal is the clock here, which can go from 0.8 to 16 MHz. Then you have the data in signal, which is used to select the input channel to convert among the eight channels available. It is a 3-bit address, which starts here at the third clock period. So if you want to select a different channel, you send the new address during this transmission here. And the sample for the new channel will be available at the next SPI transmission here. And the last signal is data out. It starts with 4 zeros, and then contains the 12-bit data from the ADC converter, which will be received by the microcontroller for digital processing with software. Let's see an example of data acquisition by capturing the SPI interface of ADC120 with an oscilloscope. From the oscilloscope, you can see the four signals of the SPI interface. And we zoom in with the horizontal scale to better see the details. Note that this is captured with analog probes. You can clearly see from the clock line in yellow that there are several SPI packets sent successively with the same channel address. In this case, by looking at the signal in red, the channel selected is channel 1. On the blue signal at the bottom, this is the 12-bit data converted by the ADC. You can notice that only the last few bits are toggling. This is because the analog signal captured in this example is almost constant. In the next section, we will see the board available to evaluate the ADC. This is a picture of the ADC120 evaluation board. The name of this board is STival-AKI001v1, and the device is located right here. This board has been designed as an expansion board to be connected to STM32 nuclear board. So it has the Morpho connector on the left and right side. And the connector to hook up the analog inputs is located at the bottom. For the online resources, let's check what is available on ST.com. From ST.com, you can look for ADC120. There you go. Then you reach the product page. If you go to resources section, you can find the datasheet and application notes. And if you go to tools and software, there you find the evaluation board. Then you reach the evaluation board page with its description. And in the resources section, you can find all the documentations. User manual, Gerber file, BOM, and schematic. The evaluation board can be used in two different ways. First case in standalone mode, in which case you need to provide an external power supply. Second case connected to STM32 nuclear board. In this case, it is power supplied by USB 5V from the nuclear board here. This USB connection enables PC communication and further signal processing. In standalone mode, the connector for the SPI interface is this one here. When attached to nuclear board, the SPI interface is directly connected to STM32 microcontroller through the Morpho connector. It is using the Pintz Cycling Green here. Now let's study the block diagram of the evaluation board. Here is the ADC120 with the eight analog inputs on one side and the SPI interface on the other side. It is powered at 3.3V thanks to a LDO regulator. For the purpose of evaluation, each channel is connected to a pre-cable function on the board in order to show different possibilities of analog signals to measure. On the first two channels, there are analog temperature sensors. It is two different types of sensors to show two different ways to measure the temperature. On channel 2, you have an amplification for strength gauge. On channel 3, you can connect an external signal from plus or minus 5V. On channel 4, there is a voltage reference. On channel 5, it is a direct connection from an external signal, nothing in between. Because the ADC is powered at 3.3V, the signal must be within the range 0V to 3.3V. And finally, on channel 6 and 7, there are user configurable filters. In the following slides, we will take a closer look at these onboard features for each channel. On channel 0, there is a temperature sensor from ST, the STLM-20. The ADC measures directly the output of the sensor, so the output voltage in volt is the image of the temperature. And the corresponding value in degree Celsius is given by a specific equation that you can find in the user manual. For example, a variation of 0.1 degree Celsius on STLM-20 represents 1.5 LSB of ADC-120. On the picture on the right, you can see the location of the sensor. On channel 1, there is another temperature sensor based on the principle to measure the resistance of a platinum element. The resistor value varies with the temperature. On the schematic, you can see that the signal is conditioned so that the resistor value will change the voltage on the ADC input. So for the PT-100 used here, it has a resistance of 100 ohm at 0 degrees Celsius. Then the relation between resistor value and temperature is given by a specific equation. On the picture, you can see that the sensor is located here. Channel 2 is used for strain gauge measurement. It is composed of a witchstone bridge and an instrumentation amplifier to amplify the strain gauge variation. So to determine the resistor value here, the ADC-120 reads the voltage image of the amplified voltage variation. For example, if we use 120 ohm resistors in the witchstone bridge with a minimal measurable variation of strain of 0.1%, thus, the voltage variation on ADC-120 input is 9 millivolts, which means 11 LSB. Note that the witchstone bridge is not directly on the eval board. It is external, but you can attach it via the connector located here. On Channel 3, the open configuration is used to rectify the external voltage in a positive range from 0V to 3.3V so that it can be used by the ADC. And the input for the external signal is located on this connector here. Channel 4 is used to measure a precise voltage reference. It is based on TS3431, which is a natural stable shunt voltage reference. It has a precision of 0.25%, and if we use it with resistors of 0.1% precision, then the output voltage will represent 6 LSB of ADC-120. On Channel 5, you have a direct connection to the ADC input. So it is the simplest way to measure an external signal with this eval board. That's why we will use this channel in the next demo. You have to connect your signal here on this connector. Just make sure the signal level is below 3.3V. The Channel 6 and Channel 7 are used for custom configurable filters. It has a resistor divider to provide an acceptable voltage range to ADC input. And it has an operational amplifier where you can set the gain. The two inputs are located here on this connector. But be careful that all the resistors here are not connected by default on the eval board. So you cannot use it directly without configuring it first for your own application. It's time to use the evaluation software and to show you a demo of the output signals you get on the eval board from all these channels. The evaluation software uses the nuclear board. So these are the boards you will need to run the demo. One ADC-120 evaluation board, one STN32 nuclear board, and one USB cable. Then you have to connect the ADC expansion board on top of the nuclear board. The software runs on the computer. So you'll need to connect each other with the USB cable. Before being able to use the nuclear board, it needs to run the right firmware to interface the SPI interface with the ADC-120 device. So step one is to flash the STN32 firmware. Let's see a quick demo on how to easily flash the STN32. So connect the USB cable to your computer. You can see here that the nuclear board appears like a virtual drive. Then open the software package for ADC-120. Inside you have the binary of STN32. And all you need to do is to copy this file and paste it in the virtual drive. And that's it, the nuclear board is flashed. Now that the hardware is ready, we can use the evaluation software on PC. So step two is to launch the software. Let's see how to use the evaluation software. Open the software package and start the program. You can see there is a main window here for the control and a console here to display information. On the main window, click to connect to connect to the nuclear board. And there you have a menu selection with several possible actions to perform with the demo. If I click on menu one, it prints the data of all channels. Then I can stop. On the left hand side here, I have the sample value for my eight channels. These are the direct values we get from the SPI interface of ADC 120. Because this is a 12-bit ADC, the maximum sample value I can get is 4095. On the right hand side here, it is the same values but converted into volts. The device is powered at 3.3 volts, so the maximum input voltage is 3.3 volts. The menu number two is similar, but it prints only one channel. So here it prints channel zero. I can stop. If I want to change the channel, I come here and I select my channel number. Let's try channel two. Print channel two. So it will just capture the channel two and print it. I can do this till the last channel. Channel seven. I can print like this continuously or stop anytime. The menu number three will plot all the channels in a more graphical way. So let's try it. There it is. And I can maximize the window. So these are the values of the eight channels on the eval board. Just write out of the box. I didn't bring any modification on the board. On channel zero and channel one, we have the temperature sensors as we expected. And we can see both sensors provide the same board temperature. On channel two, it is a strain gauge input. And on channel three, an external signal which can have a negative range. But I have nothing connected on these two inputs. So it just shows the default voltage value of the board. On channel four, there is a voltage reference, which is precisely at 1.70 volts. On channel five, it is a direct connection to the analog signal. I have nothing connected at the moment, but what I can do is to connect a jumper to for the input to ground. So let's try it. I put the jumper. And as you can see now, the ADC measures zero volts because it is to ground. On channel six and channel seven, the components for filtering on dot soldered. So the value it shows on dot meaningful. Money number four is to capture the data and save them into a file. So I click to start the capture. Now I can record over a long period of time the evolution of an analog signal, which changes slowly like the temperature, for instance. And when I'm done, I can press stop. Then I can go to the program location to get the file. In the file, I see the digital sample value of all the channels here, channel zero to channel seven. The data converted into volt here and even the corresponding temperature value of the first two channels. With all this data, I can now analyze them and maybe do some post processing. Money number five is similar to number four, but it will only record one channel. And I can select the channel I want to record here. Let's try channel four. I capture this channel. Then I can stop. And I will find the data recorded here. All the data captured by the ADC that we have seen so far in the software demo look pretty static. This is because there are no dynamic signals by default on the eval board. They need to be brought by the user. So let's generate easily an analog signal which evolves a bit faster. To do that, we will use the STM32 microcontroller. This is a typical block diagram of what you can find inside a STM32. And the STM32 we have on the nuclear board embeds a digital to analog converter. So we will use this analog block to generate a sine wave. This is the sine wave generated by STM32 thanks to its D2A converter. We selected a slow frequency on purpose for this waveform to have the time to see it and to capture it. The sine wave is generated on a specific output pin named PA4. So you need to connect this signal to the input of our ADC on channel 5 with a wire. Like you can see on the picture so you have to connect the wire from here, PA4 to here in 5. Now we can try to capture this generated signal with the evaluation tool. I come back to the software and I use menu 3 to plot the signal. And there, on channel 5 I can see my sine wave captured. Because the plotting on this window is slow at only 2 samples per second it is good that the waveform is changing slowly for the purpose of this demo. But what about capturing a faster signal? A simple way to get a faster and periodic signal is to use the probe compositor signal which is available on every oscilloscope usually located on the side. The frequency is 1kHz and the amplitude 2.5V. So you connect the ground to one of the ground connector of the nuclear board and the oscilloscope signal to the input channel 5. What will happen if I try to capture this signal with the evaluation tool? I am back on the software and I use again the menu number 3 to plot the signal. On channel 5 where is connected the signal I can see it is oscillating between 0V and 2.5V. But I cannot see the square waveform because the 1kHz signal is too fast to be captured with this window. That's why I will use another menu to capture the signal faster. Menu number 6 here will capture the signal for a short time faster at 20kHz. So let's try. This menu only capture one channel so I need to select first the channel I want to capture channel 5. Then I can press the button and start the capture. So I can see here it has captured 1000 samples in 50ms. Now let's open the file. Here are all the samples saved at 20kHz. With Excel I can quickly analyze the data by plotting them. Let's zoom a little bit and there you go. I can see my square waveform at 1kHz here with an amplitude of 2.5V. So this is a way to capture fast signals on ADC120 evaluation board. And I can even capture at 100kHz by using the last menu selection. You can get more information for this product on ST.com. Thank you for watching.