Africa's Talking v1 R1 Dev Kit MQTT (SIM 800L) 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 yoiur Africa's Talking Device Group and Password

#define MQTT_USERNAME "<Africa's Talking app username>"

#define MQTT_DEVICE_GROUP "<User Device Group>"

#define MQTT_PASSWORD "<Device Group Password>" // 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 "<Chosen Client ID>" // 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.{*}