USB Serial - differences between WIFI and MINIMA #82
Description
There API differences between the Serial objects on the WIFI and MINIMA.
Sorry, it is unclear to me if this should be an issue here, as code compiles on one and not the other. Or should be a discussion on the forum.
The following sketch, which is a slightly modified version of the USBToSerial Teensy example sketch, builds and runs fine on MINIMA, but compiler errors with WIFI. Note: code will not properly on current released code as availableForWrite() was not implemented and uses the default implementation which returns 0.
/* USB to Serial - Teensy becomes a USB to Serial converter
http://dorkbotpdx.org/blog/paul/teensy_as_benito_at_57600_baud
You must select Serial from the "Tools > USB Type" menu
This example code is in the public domain.
*/
// set this to the hardware serial port you wish to use
#if defined(ARDUINO_UNOR4_WIFI)
UART _UART4_(18, 19);
#define SerialX Serial3
#else
UART _UART2_(18, 19);
#define SerialX Serial2
#endif
#define HWSERIAL Serial1
unsigned long baud = 115200;
const int reset_pin = 4;
void setup()
{
pinMode(LED_BUILTIN, OUTPUT);
pinMode(3, OUTPUT);
pinMode(4, OUTPUT);
pinMode(5, OUTPUT);
pinMode(6, OUTPUT);
pinMode(7, OUTPUT);
pinMode(8, OUTPUT);
digitalWrite(LED_BUILTIN, LOW);
digitalWrite(reset_pin, HIGH);
pinMode(reset_pin, OUTPUT);
Serial.begin(baud); // USB, communication to PC or Mac
HWSERIAL.begin(baud); // communication to hardware serial
}
long led_on_time=0;
byte buffer[80];
unsigned char prev_dtr = 0;
void loop()
{
unsigned char dtr;
int rd, wr, n;
// check if any data has arrived on the USB virtual serial port
rd = Serial.available();
if (rd > 0) {
// check if the hardware serial port is ready to transmit
wr = HWSERIAL.availableForWrite();
if (wr > 0) {
// compute how much data to move, the smallest
// of rd, wr and the buffer size
if (rd > wr) rd = wr;
if (rd > 80) rd = 80;
// read data from the USB port
n = Serial.readBytes((char *)buffer, rd);
// write it to the hardware serial port
HWSERIAL.write(buffer, n);
// turn on the LED to indicate activity
digitalWrite(LED_BUILTIN, HIGH);
led_on_time = millis();
}
}
// check if any data has arrived on the hardware serial port
rd = HWSERIAL.available();
if (rd > 0) {
// check if the USB virtual serial port is ready to transmit
wr = Serial.availableForWrite();
if (wr > 0) {
// compute how much data to move, the smallest
// of rd, wr and the buffer size
if (rd > wr) rd = wr;
if (rd > 80) rd = 80;
// read data from the hardware serial port
n = HWSERIAL.readBytes((char *)buffer, rd);
// write it to the USB port
Serial.write(buffer, n);
// turn on the LED to indicate activity
digitalWrite(LED_BUILTIN, HIGH);
led_on_time = millis();
}
}
// check if the USB virtual serial port has raised DTR
dtr = Serial.dtr();
if (dtr && !prev_dtr) {
digitalWrite(reset_pin, LOW);
delayMicroseconds(250);
digitalWrite(reset_pin, HIGH);
}
prev_dtr = dtr;
// if the LED has been left on without more activity, turn it off
if (millis() - led_on_time > 3) {
digitalWrite(LED_BUILTIN, LOW);
}
// check if the USB virtual serial wants a new baud rate
if (Serial.baud() != baud) {
baud = Serial.baud();
if (baud == 57600) {
// This ugly hack is necessary for talking
// to the arduino bootloader, which actually
// communicates at 58824 baud (+2.1% error).
// Teensyduino will configure the UART for
// the closest baud rate, which is 57143
// baud (-0.8% error). Serial communication
// can tolerate about 2.5% error, so the
// combined error is too large. Simply
// setting the baud rate to the same as
// arduino's actual baud rate works.
HWSERIAL.begin(58824);
} else {
HWSERIAL.begin(baud);
}
}
}
The difference to the actual example is I added a bunch of pinMode statements to enable some debugging of my updated code base and I setup to allow optional Serial object using the SCL/SDA pins.
Compiler errors on the WIFI board:
C:\Users\kurte\Documents\Arduino\R4-Uno-wifi\USBtoSerial_r4\USBtoSerial_r4.ino: In function 'void loop()':
C:\Users\kurte\Documents\Arduino\R4-Uno-wifi\USBtoSerial_r4\USBtoSerial_r4.ino:92:16: error: 'class UART' has no member named 'dtr'
dtr = Serial.dtr();
^~~
C:\Users\kurte\Documents\Arduino\R4-Uno-wifi\USBtoSerial_r4\USBtoSerial_r4.ino:106:14: error: 'class UART' has no member named 'baud'
if (Serial.baud() != baud) {
^~~~
C:\Users\kurte\Documents\Arduino\R4-Uno-wifi\USBtoSerial_r4\USBtoSerial_r4.ino:107:19: error: 'class UART' has no member named 'baud'
baud = Serial.baud();
^~~~
exit status 1
Compilation error: 'class UART' has no member named 'dtr'
Notes/Questions - things to try.
MINIMA:
- Does the MINIMA code pickup baud rate changes, with the baud() method? I have not tried to see yet.
- Does it reflect it back to the host?
- Does the Serial monitor care what the baud rate is set to? As it sends and receives at USB speed
WIFI:
-
baud(). Could either make Serial object, as a sub-class of the UART code, or could add baud() to the UART code, or could punt.
-
How are the communications between ESP32 and hardware UART impacted by what BAUD rate chosen? Does it change the speed between the two processors, I pretty sure YES. but could instead choose to use some fixed speed.
-
And if I do Serial.begin(new_baud_rate) is that communicated back to ESP32? And then back to the host?