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UART Baud Rate on an nRF52840
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Please be positive and constructive with your questions and comments.

UART Baud Rate on an nRF52840

by sminogue on Sat Oct 16, 2021 9:17 am

Is it possible to increase the baud rate on the BLEUart service on the nrf52840?
I found:
https://infocenter.nordicsemi.com/index ... _958674283
Which to me says the hardware should be able to handle up to 1mbps

Then I found:
https://learn.adafruit.com/introducing- ... d/hardware

Admittedly this is for the 51822 but I would think it should be doable on a later generation 52840 (assuming those numbers are increasing with release).

What I dont understand is how I actually do: "AT+BAUDRATE=115200" to set the baud rate in code.

sminogue
 
Posts: 35
Joined: Sun Oct 04, 2020 9:35 am

Re: UART Baud Rate on an nRF52840

by mikeysklar on Mon Oct 18, 2021 6:23 pm

@sminogue,

Are you using an Adafruit Feather nRF52840?

Are you running Arduino or CircuitPython?

mikeysklar
 
Posts: 6236
Joined: Mon Aug 01, 2016 8:10 pm

Re: UART Baud Rate on an nRF52840

by sminogue on Mon Oct 18, 2021 9:32 pm

Yes I am using an nRF52840 and I am writing my code in C++ in the Arduino IDE.

sminogue
 
Posts: 35
Joined: Sun Oct 04, 2020 9:35 am

Re: UART Baud Rate on an nRF52840

by mikeysklar on Tue Oct 19, 2021 6:35 pm

It scanned the Adafruit nRF52 Arduino library and it looks like you specify the desired baudrate with the begin() statement. I believe 921,600 is the max value supported.

Code: Select all | TOGGLE FULL SIZE
// Configure and Start BLE Uart Service
  bleuart.begin(921600);



https://github.com/adafruit/Adafruit_nRF52_Arduino
https://github.com/adafruit/Adafruit_nR ... leuart.ino

Code: Select all | TOGGLE FULL SIZE
/*********************************************************************
 This is an example for our nRF52 based Bluefruit LE modules

 Pick one up today in the adafruit shop!

 Adafruit invests time and resources providing this open source code,
 please support Adafruit and open-source hardware by purchasing
 products from Adafruit!

 MIT license, check LICENSE for more information
 All text above, and the splash screen below must be included in
 any redistribution
*********************************************************************/
#include <bluefruit.h>
#include <Adafruit_LittleFS.h>
#include <InternalFileSystem.h>

// BLE Service
BLEDfu  bledfu;  // OTA DFU service
BLEDis  bledis;  // device information
BLEUart bleuart; // uart over ble
BLEBas  blebas;  // battery

void setup()
{
  Serial.begin(115200);

#if CFG_DEBUG
  // Blocking wait for connection when debug mode is enabled via IDE
  while ( !Serial ) yield();
#endif
 
  Serial.println("Bluefruit52 BLEUART Example");
  Serial.println("---------------------------\n");

  // Setup the BLE LED to be enabled on CONNECT
  // Note: This is actually the default behavior, but provided
  // here in case you want to control this LED manually via PIN 19
  Bluefruit.autoConnLed(true);

  // Config the peripheral connection with maximum bandwidth
  // more SRAM required by SoftDevice
  // Note: All config***() function must be called before begin()
  Bluefruit.configPrphBandwidth(BANDWIDTH_MAX);

  Bluefruit.begin();
  Bluefruit.setTxPower(4);    // Check bluefruit.h for supported values
  //Bluefruit.setName(getMcuUniqueID()); // useful testing with multiple central connections
  Bluefruit.Periph.setConnectCallback(connect_callback);
  Bluefruit.Periph.setDisconnectCallback(disconnect_callback);

  // To be consistent OTA DFU should be added first if it exists
  bledfu.begin();

  // Configure and Start Device Information Service
  bledis.setManufacturer("Adafruit Industries");
  bledis.setModel("Bluefruit Feather52");
  bledis.begin();

  // Configure and Start BLE Uart Service
  bleuart.begin();

  // Start BLE Battery Service
  blebas.begin();
  blebas.write(100);

  // Set up and start advertising
  startAdv();

  Serial.println("Please use Adafruit's Bluefruit LE app to connect in UART mode");
  Serial.println("Once connected, enter character(s) that you wish to send");
}

void startAdv(void)
{
  // Advertising packet
  Bluefruit.Advertising.addFlags(BLE_GAP_ADV_FLAGS_LE_ONLY_GENERAL_DISC_MODE);
  Bluefruit.Advertising.addTxPower();

  // Include bleuart 128-bit uuid
  Bluefruit.Advertising.addService(bleuart);

  // Secondary Scan Response packet (optional)
  // Since there is no room for 'Name' in Advertising packet
  Bluefruit.ScanResponse.addName();
 
  /* Start Advertising
   * - Enable auto advertising if disconnected
   * - Interval:  fast mode = 20 ms, slow mode = 152.5 ms
   * - Timeout for fast mode is 30 seconds
   * - Start(timeout) with timeout = 0 will advertise forever (until connected)
   *
   * For recommended advertising interval
   * https://developer.apple.com/library/content/qa/qa1931/_index.html   
   */
  Bluefruit.Advertising.restartOnDisconnect(true);
  Bluefruit.Advertising.setInterval(32, 244);    // in unit of 0.625 ms
  Bluefruit.Advertising.setFastTimeout(30);      // number of seconds in fast mode
  Bluefruit.Advertising.start(0);                // 0 = Don't stop advertising after n seconds 
}

void loop()
{
  // Forward data from HW Serial to BLEUART
  while (Serial.available())
  {
    // Delay to wait for enough input, since we have a limited transmission buffer
    delay(2);

    uint8_t buf[64];
    int count = Serial.readBytes(buf, sizeof(buf));
    bleuart.write( buf, count );
  }

  // Forward from BLEUART to HW Serial
  while ( bleuart.available() )
  {
    uint8_t ch;
    ch = (uint8_t) bleuart.read();
    Serial.write(ch);
  }
}

// callback invoked when central connects
void connect_callback(uint16_t conn_handle)
{
  // Get the reference to current connection
  BLEConnection* connection = Bluefruit.Connection(conn_handle);

  char central_name[32] = { 0 };
  connection->getPeerName(central_name, sizeof(central_name));

  Serial.print("Connected to ");
  Serial.println(central_name);
}

/**
 * Callback invoked when a connection is dropped
 * @param conn_handle connection where this event happens
 * @param reason is a BLE_HCI_STATUS_CODE which can be found in ble_hci.h
 */
void disconnect_callback(uint16_t conn_handle, uint8_t reason)
{
  (void) conn_handle;
  (void) reason;

  Serial.println();
  Serial.print("Disconnected, reason = 0x"); Serial.println(reason, HEX);
}

mikeysklar
 
Posts: 6236
Joined: Mon Aug 01, 2016 8:10 pm

Re: UART Baud Rate on an nRF52840

by sminogue on Tue Oct 19, 2021 7:48 pm

Results in a compile error:

error: no matching function for call to 'BLEUart::begin(int)'

I'm looking through the code in
https://github.com/adafruit/Adafruit_nR ... LEUart.cpp
https://github.com/adafruit/Adafruit_nR ... /BLEUart.h

And dont see a begin with a parameter.

sminogue
 
Posts: 35
Joined: Sun Oct 04, 2020 9:35 am

Re: UART Baud Rate on an nRF52840

by mikeysklar on Wed Oct 20, 2021 9:49 am

@sminogue,

Good point.

I don't see a way to set the BLE UART baudrate. I think the following only works for the nRF52 hardware UARTs (non-BLE).

https://github.com/adafruit/Adafruit_nR ... q=baudrate

C5C7A303-BCAE-4BDD-8C60-EAB25040FA37.jpeg
C5C7A303-BCAE-4BDD-8C60-EAB25040FA37.jpeg (206.11 KiB) Viewed 55 times


I would suggest opening an issue and requesting a setable BLE UART. If there is a way that will come out of the issue.

https://github.com/adafruit/Adafruit_nR ... ino/issues

mikeysklar
 
Posts: 6236
Joined: Mon Aug 01, 2016 8:10 pm

Please be positive and constructive with your questions and comments.