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I2C with DMA not working

sadeepTA
Associate II

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);
}

1 ACCEPTED SOLUTION

Accepted Solutions

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

If you feel a post has answered your question, please click "Accept as Solution".

View solution in original post

11 REPLIES 11

I2C without DMA works?

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

What are values of pullup resistors?

JW

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?

 

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?

Tips, Buy me a coffee, or three.. PayPal Venmo
Up vote any posts that you find helpful, it shows what's working..

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

If you feel a post has answered your question, please click "Accept as Solution".

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. 

Tips, Buy me a coffee, or three.. PayPal Venmo
Up vote any posts that you find helpful, it shows what's working..

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

No, I'm learning this on my own.

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


@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:

AndrewNeil_0-1719829612358.png

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:

AndrewNeil_1-1719830026827.png

 

 

#Pullups #I2CPullups

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

If you feel a post has answered your question, please click "Accept as Solution".