Africa's Talking v1 R2 Dev Kit MQTT Sample for STM32CubeIDE

• See overrall config as shown below

• Set HSE to Crystal/Ceramic Resonator and disable LSE as shown

• Set serial mode to Asynchronous for both USART1 and USART2 and ensure gloabl interrupt is enabled under NVIC Settings

Clock Configuration

• See below clock configuration.

  • Toggle PLL and PLLCLK
  • Set input frequency to 8Mhz

• You might want to set the multiplier PLLMul to 11 or above then click Resolve Clock Issues

Project Management

• Under Project Manager ensure Generate peripheral initialization... is checked

• Then inside Advanced Settings Set USART driver to LL
  

SAVE AND GENERATE PROJECT

Important

• Inside ./Core/Inc/main.h ensure you have chaged the MQTT-Specific settings with your Africa's Talking Device Group and Password

#define MQTT_USERNAME "<CoolPerson>"

#define MQTT_DEVICE_GROUP "<cooldevicegroup>"

#define MQTT_PASSWORD "<strongpassword>" // Mandatory field

#define AUTH_CREDENTIALS MQTT_USERNAME ":" MQTT_DEVICE_GROUP // Mandatory field; resolves to username:devicegroup

#define MQTT_QOS 1 // Can be 0 or 1 or 2

#define DEVICE_ID "Eris" // Mandatory Field

• Note that you can add new subscription callbacks or modifiy the subscription callback to do something else. See ./Core/Src/main.c

void downStreamCommandHandler(MessageData *messageData)
{
  serialPrint("Received a message %s : \r\n", messageData->message->payload);
  serialPrint("Topic is %s \r\n", messageData->topicName);
  memset((char *)messageData->message->payload, '\0', sizeof(uint8_t));
  memset((char *)messageData->topicName, '\0', sizeof(uint8_t));
  serialPrint("Sending message \r\n");

  char dataMessage[100];
  mqttMessage.dup = 0;
  mqttMessage.qos = MQTT_QOS;
  mqttMessage.id = 0;
  mqttMessage.retained = 0;
  mqttMessage.payload = dataMessage;
  sprintf(dataMessage, "test");
  mqttMessage.payloadlen = strlen((char *)mqttMessage.payload) + 1;
  if (MQTTPublish(&mqttClient, (char *)DEVICE_UPSTREAM_TOPIC, &mqttMessage) == 0)
  {
    serialPrint("Message published \r\n");
  }
  else
  {
    serialPrint("Unable to publish message \r\n");
    sent_failed_count++;
  }
}

• See the APN configuration inside ./Core/Src/main.c

• Note that the line shown below is commented under ./Core/Src/syscalls.c

extern int __io_putchar(int ch) __attribute__((weak)); 

• Also note that an IRQ handler is required for USART1; see ./Core/Src/stm32f1xx_it.c.

• Note the differences under ./Core/{*}/usart.{*}

Fun Excercises

• Prevent the device from republishing the birth message when connected.
• Repurpose the downStreamCommandHandler(MessageData *messageData) to blink the LED PC13 (enabled) for a number of times (N) for (X) seconds when (N,X) is sent to it under the <username>/<devicegroup>/Eris/rec topic.
• Confirm that you can receive the will message when disconnected.

Troubleshooting

• If the hardware fails to connect to the GSM network within 30 seconds,
  1. Give it more time, the program will try to restart the GSM module
  2. Manually reset the board
  3. Your USB host might not be delivering sufficient power or you're using a longer cable