How to change and reset the Alarm Function in the MAX35103?

After an alarm event occurs, you will need to read the interrupt status register in order to clear it but you will also need to clear the control register (0xFFh) bit Alarm Flag Arm. This bit must be written to 0 to rearm the alarm and it goes to 1 at the same time as the AF bit in the interrupt register. Once the alarm has been fully reset the alarm registers RTC_match and RTC_ctrl can be changed.

What are some things to check if the crystal on the MAX35103 is not starting up?

The crystal not starting up can be the result of many different things including but not limited to: Improper layout of traces leading from the MAX35103 to the crystal oscillator. If the traces run parallel and close to each other, there may be some parisitic capacitance added into the traces that would prevent the crystal from oscillating. Incorrect oscillator is chosen to work with the MAX35103. Please refer to the product datasheet for a chosen oscillator and compare them to the recommended values for oscillator capacitance and etc. in the MAX35103 datasheet. Please refer to the way that the traces between the MAX35103 and the crystal oscillator are routed in the MAX35103EVKIT for a good example to follow.

Is the MAX35101EVKIT default configuration file also compatible with the MAX35103EVKIT?

The MAX35101EVKIT default configuration file is not compatible with the MAX35103EVKIT. Instead of using a default config file for the MAX35103EVKIT, simply have the client launch the application and create a new configuration. There really is not a reasonable default since most of the settings are specific to the flow tube and transducers the client is using and these items are not part of the EVKIT.

Can MAX35103 EVKIT be connected to the MCU board of the user for testing?

Yes. There is an SPI interface that comes out of the MAX35103EVKIT board, which can be conveniently connected to other MCUs. There is a DIP switch on the board which can disconnect the electrical connection between MAX35103 and MCU on the board. The SPI inputs to the slave device, if using other MCUs, are CE NOT, SCK, DIN, and DOUT.

How do I convert the TOF measured by MAX35103 to flow rate?

The flow rate measurement setup for the transducers is as follows: Downstream ultrasonic signal propagation time equation: Upstream ultrasonic signal propagation time equation: Where C0 is the velocity of propagation in the medium and is considered to be constant, and v is the flow rate. Subtract Equation 2 from Equation 1 and simplify to obtain the flow rate:

We have purchased a MAX35103evkit to get an idea producing an ultrasonic flow meter using MAX35103. As we are using 2Mhz piezo sensor with it. How can we configure 2MHz sensor with the kit?

Please be advised that MAX35103 was designed for a 4MHz resonator. No other frequency of resonator is supported. Also, the drive frequency is adjusted with the ‘Pulse Launch Divider’ (DPL[3:0]) bits in the TOF1 Register, can only provide 125kHz to 1MHz pulse launch frequencies as below: So we can not use MAX35103 to support 2MHz sensor. Sorry about this.

What are the differences between the two MAX35103 EVKITs?

There are two different evaluation kits for the MAX35103: the MAX35103EVKIT# and the MAX35103EVKIT2#. While they both include the MAX35103, the features of the EVKITs are different. The MAX35103EVKIT# comes with a PC software tool designed to help you configure the chip for your own flow meter hardware. The board is highly configurable, and it should be used to evaluate the MAX35103 for a specific application. The MAX35103EVKIT2# is an application example intended as an off-the-shelf flow-metering solution. That said, it can be useful as a prototyping platform for some applications, but it is not nearly as configurable as the MAX35103EVKIT#. You can program the micro on this kit via JTAG, but it will not work with the PC software tool used with the MAX35103EVKIT#. The MAX35103EVKIT2# comes with pre-loaded firmware for flow-metering.

Why is the time measurement accuracy specification in the EC table of MAX35101, MAX35102, MAX35103 typically 20 ps while the absolute ToF Error in TOCs are in the order of tens of nanoseconds?

Absolute TOF is a time measurement made in a single direction. Time Measurement Accuracy (TACC) has to do with differential time measurement which is the difference between time adjacent “up” and “down” absolute TOF’s. Much of the time error internal to the TDC is due to electrical path delays. These delays mostly cancel in the subtraction required to arrive at a delta TOF. Absolute TOF isn’t relevant to a flow measurement application. TACC is relevant to flow measurement applications because it is the delta TOF that is used to determine flow rate. Absolute TOF is relevant to pulse-echo applications.