I2C with DMA not working

[sadeepTA]

Hi,

I'm somewhat new to STM32. I need to use DMA to collect data from a tempreture sensor over I2C.

My sensor is an Adafruit MCP 9600 and I'm using a Nucleo F446RE board. Following is the code I use. Can someone help as I've been stuck here for days without knowing what to do. 

uint8_t TMP_ADDR = 0x65 << 1;
uint8_t TMP_REG = 0x00;
uint8_t TempReading[100];

void MCP9600_ReadTemperatureDMA(void)
{
TempReading[0] = TMP_REG;
if (HAL_I2C_Master_Transmit(&hi2c1, TMP_ADDR, TempReading, 1, HAL_MAX_DELAY) == HAL_OK) {
if (HAL_I2C_Master_Receive_DMA(&hi2c1, TMP_ADDR, TempReading, sizeof(TempReading)) == HAL_OK) {
HAL_GPIO_WritePin(LD2_GPIO_Port, LD2_Pin, GPIO_PIN_SET);
}
}
}

// I2C DMA Transfer Complete Callback
void HAL_I2C_MemRxCpltCallback(I2C_HandleTypeDef *hi2c)
{
HAL_GPIO_WritePin(LD2_GPIO_Port, LD2_Pin, GPIO_PIN_RESET);
}

[waclawek.jan]

I2C without DMA works?

Start perhaps with bit-banged I2C to check if the connections are OK.

What are values of pullup resistors?

JW

[sadeepTA]

hey,

Thanks for the reply.

1. Yes. it works and gives me tepreture reading.

2. I am not using any external pullups. Am I supposed to use it like that?

[Tesla DeLorean]

I2C typically expects them. Internal pull-ups on STM32 pretty weak and slow, especially if presented a relatively large capacitive load..

Get a scope or logic analyzer on the signals to better understand what's happening.

You work with people with related competencies? Manager, supervisor, colleagues?

[Techn]

Can you try with Normal dma setting. You are triggering dma every time. 

[Tesla DeLorean]

DMA and IT routines return immediately,  watch for error returns and longevity of data contexts/scope passed to routines. ie not auto/local to calling subroutine. 

[sadeepTA]

Thank you for the answer. I will try with external pullups. 

No, I'm learning this on my own.

[sadeepTA]

Thanks for the reply. But can you please explain it a little bit more?

[Andrew Neil]

---

@sadeepTA wrote:

2. I am not using any external pullups. Am I supposed to use it like that?

---

Pullups are fundamental to the operation of I2C.

I2C basics: https://community.st.com/t5/stm32-mcus-products/i2c-interface-with-adxl345-using-stm32f446re/m-p/658323/highlight/true#M240123 

---

@sadeepTA wrote:

My sensor is an Adafruit MCP 9600

---

The MCP9600 is a Microchip product: https://www.microchip.com/en-us/product/mcp9600

I presume you mean this Adafruit "breakout board" - which features the Microchip MCP9600:

https://learn.adafruit.com/adafruit-mcp9600-i2c-thermocouple-amplifier 

So the question becomes: does that board provide the required pullups?

The schematics are here:

https://learn.adafruit.com/adafruit-mcp9600-i2c-thermocouple-amplifier/downloads

and show that pullups are, indeed, provided on the board:

#Pullups #I2CPullups

[Techn · Accepted solution]

There is option in Mx tool , open ioc file. Look for dma type , select normal.