Hi,
I am trying to make a program for the NRF51 development kit on mbed. I have been able to take ADC samples at 1000Hz which is what I want, but I can't seem to print the actual voltage over BLE UART on my phone. I am new to this type of thing altogether and don't know how to really print/write anything over BLE. The code below prints out a string every time ADC is called, but I don't really understand how to print out the actual ADC value over BLE which is a float.
Thanks
#include "mbed.h"
#include "BLE.h"
#include "UARTService.h"
#define NEED_CONSOLE_OUTPUT 1 /* Set this if you need debug messages on the console;
* it will have an impact on code-size and power consumption. */
#if NEED_CONSOLE_OUTPUT
#define DEBUG(STR) { if (uart) uart->write(STR, strlen(STR)); }
#else
#define DEBUG(...) /* nothing */
#endif /* #if NEED_CONSOLE_OUTPUT */
BLE ble;
Ticker t;
static float value; // stored voltage reading from ADC
Ticker ledticker; //ticker to turn on and off LED to ensure system is working properly
float Vref = 1.2; //float for reference voltage
UARTService *uart;
void disconnectionCallback(const Gap::DisconnectionCallbackParams_t *params)
{
DEBUG("Disconnected!\n\r");
DEBUG("Restarting the advertising process\n\r");
ble.startAdvertising();
}
/* Functio for initalizing ADC Configuration */
void my_analogin_init(void)
{
/* Function for Enabling ADC Initialization to 10bits, 1.2V Internal reference, OneThird Prescaling, at analog pin1
* with no external reference voltage */
NRF_ADC->ENABLE = ADC_ENABLE_ENABLE_Enabled;
NRF_ADC->CONFIG = (ADC_CONFIG_RES_10bit << ADC_CONFIG_RES_Pos) | //Configure Resolution to 10 bits
(ADC_CONFIG_INPSEL_AnalogInputOneThirdPrescaling << ADC_CONFIG_INPSEL_Pos) | //Configure ADC input selection and prescalar settings
//Internal reference voltage of 1.2V. Onethird prescaling -> 3.6V
(ADC_CONFIG_REFSEL_VBG << ADC_CONFIG_REFSEL_Pos) | //ADC reference selection to internal 1.2V VBG
(ADC_CONFIG_PSEL_AnalogInput1 << ADC_CONFIG_PSEL_Pos) | //Select Pin to be used as ADC input pin -> Disable analog pins
(ADC_CONFIG_EXTREFSEL_None << ADC_CONFIG_EXTREFSEL_Pos); //Select external reference pin -> No external reference (we use internal reference of 1.2V)
}
/* Callback function for taking ADC Sample */
void my_analogin_read_u16(void)
{
NRF_ADC->CONFIG &= ~ADC_CONFIG_PSEL_Msk; // Check if Analog input pin has been selected
NRF_ADC->CONFIG |= ADC_CONFIG_PSEL_AnalogInput1 << ADC_CONFIG_PSEL_Pos; //Check if Analog Input pin has been selected
NRF_ADC->TASKS_START = 1;
while (((NRF_ADC->BUSY & ADC_BUSY_BUSY_Msk) >> ADC_BUSY_BUSY_Pos) == ADC_BUSY_BUSY_Busy) {} //Produce ADC value only when ADC is not busy
value = (uint16_t) NRF_ADC -> RESULT;
value = (value * Vref ) /1024; //returns voltage from range of (0 to 3.6V)
DEBUG("Value = \n\r");
}
int main(void)
{
ble.init();
ble.onDisconnection(disconnectionCallback);
uart = new UARTService(ble);
/* setup advertising */
ble.accumulateAdvertisingPayload(GapAdvertisingData::BREDR_NOT_SUPPORTED);
ble.setAdvertisingType(GapAdvertisingParams::ADV_CONNECTABLE_UNDIRECTED);
ble.accumulateAdvertisingPayload(GapAdvertisingData::SHORTENED_LOCAL_NAME,
(const uint8_t *)"BLE UART", sizeof("BLE UART") - 1);
ble.accumulateAdvertisingPayload(GapAdvertisingData::COMPLETE_LIST_128BIT_SERVICE_IDS,
(const uint8_t *)UARTServiceUUID_reversed, sizeof(UARTServiceUUID_reversed));
ble.setAdvertisingInterval(160); /* 100ms; in multiples of 0.625ms. */
ble.startAdvertising();
my_analogin_init(); //Initialize ADC settings
t.attach_us(&my_analogin_read_u16,1000); //repeatedly read voltage every 1000us or every millisecond.
/* Infinite Loop*/
while(true)
{
ble.waitForEvent();
}
}
