76 lines
1.1 KiB
C++
76 lines
1.1 KiB
C++
#include "mhz19c.hpp"
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MHZ19C::MHZ19C(UART_HandleTypeDef* huart)
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: uart(huart)
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{
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rxDoneSem = xSemaphoreCreateBinary();
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BuildReadFrame();
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}
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void MHZ19C::BuildReadFrame()
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{
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txFrame[0] = 0xFF;
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txFrame[1] = 0x01;
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txFrame[2] = 0x86;
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txFrame[3] = 0x00;
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txFrame[4] = 0x00;
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txFrame[5] = 0x00;
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txFrame[6] = 0x00;
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txFrame[7] = 0x00;
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txFrame[8] = Checksum(txFrame);
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}
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uint8_t MHZ19C::Checksum(uint8_t* data)
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{
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uint8_t sum = 0;
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for(int i = 1; i < 8; i++)
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{
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sum += data[i];
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}
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return 0xFF - sum + 1;
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}
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bool MHZ19C::ReadCO2(uint16_t& ppm)
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{
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HAL_UART_Transmit(uart, txFrame, 9, 100);
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HAL_UART_Receive_DMA(uart, rxFrame, 9);
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if(xSemaphoreTake(rxDoneSem, pdMS_TO_TICKS(200)) != pdTRUE)
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{
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return false;
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}
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if(rxFrame[0] != 0xFF)
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{
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return false;
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}
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ppm = (rxFrame[2] << 8) | rxFrame[3];
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return true;
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}
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void MHZ19C::CalibrateZero()
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{
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uint8_t cmd[9] =
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{
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0xFF,
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0x01,
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0x87,
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0,
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0,
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0,
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0,
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0,
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0
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};
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cmd[8] = Checksum(cmd);
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HAL_UART_Transmit(uart, cmd, 9, 100);
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}
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