How to read data from micro USB port using Serial.read()

Firmware
1

I have a Photon with external power and am trying to read data from a serial to USB cable + OTG adapter (Serial1 is not available as it is being used for another purpose).

I have experience reading data with an RS232 TLL using Serial1.readStringUntil(), but I’m struggling to get any kind of reading. Is this not possible, or am I doing something wrong? My code below, I am still new to C so I admit I don’t really know what I’m doing when it comes to char.

Thank you!

String string;
String usbstring;
String usbstring2;

void setup(){
    Serial.begin(9600); // micro usb port
    Serial1.begin(9600, SERIAL_7E1); // TTL
}

void loop(){
    
    if (Serial.available() > 0) {                 
        char inchar = (char)Serial.read();         
        usbstring += inchar;
        Particle.publish("char",String(inchar));
        if (inchar == '\n') {                     
            Particle.publish("fullstring", usbstring);   
        }
        
    usbstring2 = Serial.readStringUntil('\r');
    Particle.publish("string2",usbstring2);        
    
    }   
}
2

What device are you trying to communicate with?
The Photon is not capable to act as a USB Serial host.

However, the Photon also features a secondary UART port Serial2 and you can also have a software serial port via ParticleSoftSerial.

1 Like
3

Thanks @ScruffR. I am trying to send data from an Android app into a Photon in a way that a) does not use Serial1 b) does not consume data operations and c) is near real-time (so preferably a hard-wired connection vs. WiFi-based).

Argon would be cleaner and enable me to interface using BLE, but it can’t do 7E1 which is required for my use case.

ParticleSoftSerial look promising, I’ll give it a try tomorrow. Thank you!

4

In what way would you need 7E1 with BLE? With BLE (and USB Serial for that matter) there is no such distinction as the "raw data" will always be packaged in a report block without start-, stop- or parity bit.
You can also use WiFi over TCP or UDP without using any data operations and shouldn't add too much latency either (can you define "nead real-time"?).

Are you writing that Android app or are you using an already written app?

1 Like
5

Sorry, I meant I would use BLE to communicate with my custom Android app, but it’s the peripheral device connected via Serial1 that requires 7E1 (which disqualifies the Argon).

Thanks for also suggesting that, I was looking at the Photon to Photon over TCP/IP examples yesterday, but given that the device will be shipped to a customer site (and given my own technical limitations), it makes me a little nervous that I’d be able to effectively troubleshoot or update if something goes wrong or changes.

When I was experimenting with using 2 Photons and publish and subscribe, I was experiencing about a 2.5-3 second latency. I think between 1-2 seconds would be ideal.

6

ParticleSoftSerial is working, thank you so much @ScruffR! I’ve now got Serial1 sending/receiving using TX/RX and 7E1, and SoftSerial also receiving from a separate peripheral on 8N1.

1 Like
7

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