i need some help understanding a specific serial port connection from a sensor. I need to read data from the sensor and make some calculations in matlab or c++ (i will decide later)
The manufacturer only gives a chart with the following details:
Sensor Serial Port
Pin Number Mode Pin Description
I Trigger Input
I RS-232 Receive
O RS-232 Transmit
PWR Sensor Power (DTR)
PWR/GND Signal Ground
Not Used (Reserved)
Not Used (Reserved)
I/O RS-485 B Signal Pin
I/O RS-485 A Signal Pin**
So my question is: OK i know that pin 2 is used to receive data but how am i going to decode the volts stream into integers for example for my program? Also, i know that pin 4 gives power to the sensor. How do i know how many volts it has to give? Generally how am i going to learn all these details since the manufacturer does not give it?
Do you think Serial Port Analyzer Software will help?
Thanks very much in advance.
You might want to search for "DE-9 pinout YourSensorNameHere" in google or This page might be of some use to you. With most RS-232 you only need pins 2,3 and 5. With out more specifics about your sensor there isn't much SO can do for you.
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I'm working on transceiving data on stm32F04xx. When I transmit data from the MCU at lower speed, it looks like if the baudrate was wrong and I get a bunch of question marks. When I increate transmission speed. I can read the data I'm sending. I've used to stm32cubeIDE to generate a simple UART code and only added
HAL_UART_Transmit(&huart2, "test\r\n", sizeof("test\r\n"), 1000);
HAL_Delay(500);
in the while loop.
On my NUCLEO-F042K6 evaluation board, I don't see any issues printing data on the tty port. But I have another device which uses the same stm32f042xx chip that only works when transmitting UART data at higher speed. so when i change my delay to something like 80 milliseconds, I can read the data flow.
I've attempted to flash the same binary that I flashed on my evaluation board on the other MCU I have but again the data only readable at higher transmission speed.
I'm flashing the MCU with stm32flash tool so I don't know if that can make a difference where on the eval board, I'm using the stm32cubeIDE to flash it.
I'm not sure what's going on here, I've tried different baudrates and different clock configurations and that doesn't seem to help too.
What could possibly cause the data to be unreadable like if the baudrate was wrong when transmitting at low speed?
I'm implementing a virtual instrument on STM32 (STM32F103x). Like a normal "hello world", I tried to start with the simplest MIDI message, sending NOTE-ON MIDI message in a loop to see if it works.
I send MIDI NOTE-ON message for every 500ms, only NOTE-ON message in a forever loop, but it not works. Is there any other MIDI message must be sent to make MIDI works? Like some initialize message?
Based on MIDI 1.0 spec, I finish my code on STM32 by sending MIDI message via USART interface.
Then use a logical analyzer, I confirmed my MIDI message is fully match the MIDI 1.0 spec. At least I believe it correct, no issue. 31250 baud rate, 1 start bit, 1 stop bit, one status message 0x92 followed by two data bytes 0x48 and 0x7F, LSB first.
Below is the NOTE-ON message captured by the logical analyzer on TX line of URAT interface. I continue send the same 3 bytes for every 500ms.
The totally time for those 3 bytes are 960 microseconds also match MIDI 1.0 spec mentioned value.
Then, based on "(CA-033) MIDI 1.0 Electrical Specification Update [2014]", I buy one 5 PIN MIDI OUT jack, connect the URAT TX line to PIN-5 through a 10 Ohm resister, connect 3.3V power to Pin-4 through a 33 Ohm resister, PIN-2 and Jack shield connect to GND. Other optional parts (buffer for Rc, ferrite beads) are not used.
However, when I use a USB-MIDI wire connect my MIDI OUT jack to my PC, nothing happen. The USB-MIDI wire has two LED indicators , one for power another for MIDI signal. After connect, the power LED is light, but the MIDI signal LED never light.
I tried to use logical analyzer to analysis PIN-5 of my MIDI OUT jack, the MIDI message byte are totally same with URAT TX line, and every 500ms one NOTE-ON message. However, it never works.
I also tried to create my own PCB with Dream SAM2695 by follow the SAM2695 Evaluation Boards. Then connect the URAT TX directly to MIDI_IN pin of SAM2695, it still no response. Since I have no confidence on my manual soldering PCB, not sure if the PCB itself has issue cause it no response. So I buy a USB-MIDI wire, but the result as I mentioned above, still no response.
======= Apr.26.2021 Update =========
Based on comments, have tried to check the output of the optocoupler.
Before do this check, I bought several BSS138 to transform the MIDI signal to 5V single use below circuit (of course change the resisters near MIDI JACK pin to 220 Ohm as the spec)
After this change I measured voltage of the 5V URAT TX, it show as 4.8+ V, and Logical Analyzer show correct MIDI note on message of this new 5V MIDI signal. However, it still not works.
The only left troubleshooting method for me is measure the output of the optocoupler on this USB-MIDI wire. But I didn't find an optocoupler on this MIDI USB wire PCB. There even do not have any one component has 4 pins on the PCB (based on my understanding, an optocoupler need at least 4 pins).
There only have one main chip on the PCB, it is possible that the optocoupler is embedded in that chip? Since the pin are too small I failed to connect my logical analyzer to those pin to check.
I am planning to develop a simple Profibus master (FDL level) in Linux, more specifically on a Raspberry Pi. I have an RS485 transceiver based on a MAX 481. The master must work on a bus where there are multiple masters.
According to the Profibus specification, you must count the number of '1' bits on the bus to determine when it is time to rotate the access token. Specifically after 11 '1' bits the next frame starts. 11 bits is also exactly one frame.
In Linux, how can I detect these 11 '1' bits? They won't be registered by the driver as there is no start bit. So I need a stream of bits, instead of decoded bytes.
What would be the best approach?
Unfortunately, making use of microcontroller/microprocessor UART is a BAD choice.
You can generate 11 bits setting START_BIT, STOP_BIT, and PARTITY_BIT (even) in your microcontroller UART peripheral. Maybe you will be lucky to receive whole bytes from a datagram without losses.
However, PROFIBUS DP datagram is up to 244 bytes and PROFIBUS DP requires NO IDLE bits between bytes during datagram transmission. You need a UART hardware or UART microcontroller peripheral with a FIFO or register that supports up to 244 bytes - Which is very uncommon, once this requirement is very specific from PROFIBUS.
Another aspect is related to the compatibility of baud rates. Usually, the whole range of PROFIBUS PD baud rates is not fully available on common microcontrollers UART.
My suggestions:
Implement this UART part on FPGA and interface with Raspberry Pi using e.g. SPI. You can decide on the extension of PROFIBUS stack portion you can 'outsource' to FPGA and the part you can keep on RPi.
Use an ASIC (maybe ASPC2, but outdated) and add another compatible processor to implement a deterministic portion of the stack. Later you can interface this processor with your RPi.
Implement using an industrial communication dedicated processor (Like TI Sitara am335x).
Let's say I am talking to a PHY chip via RGMII.
What is the relationship between the serial information transmitted on the RGMII to the signals that go out to the MDI?
I understood from the timing diagram of RGMII that the rising edge is 4 bits and the falling edge is 4 bits. So for each clock that gives 8 bits.
For 100Mbps, the clock required is 25MHz. So for every 25MHz clock cycle, 8 bits are transmitted.
Does the PHY chip simply send each 8 bits over the MDI immediately?
If that is the case, then how do I correctly package these serial 8 bits of data into a proper ethernet frame?
I a trying to troubleshoot a piece of hardware where the PHY does not work properly but the only way troubleshoot is if I can control the RGMII. However, I do not understand this relationship between the RGMII and how it affects the MDI.
I presume that if I look at wireshark, it will not show any packets of information unless I send a string of serialized data in a proper Ethernet frame.
The PHY should have some documentation and sample code. Without, finding out how exactly it works can be a very tedious task.
You can find the general RGMII description here: https://web.archive.org/web/20160303212629/http://www.hp.com/rnd/pdfs/RGMIIv1_3.pdf
Im trying to connect a MMA852Q accellerometer to a 18F2550 microcontroller. According to accellerometer datasheet i2c clock and data lines would not tolerate voltages more than 1.6- 3.7 (+0.3). Those lines have to be pulled up to 5v for microcntroller to work. Im new in to this subject and your advice to overcome this issue would be really helpful.
You could look for "I2C level shifter" for attaching buses with different voltages together.
NXP appnote 10441 (pdf) has a very neat generic one, for example.