# Arduino Uno with Texas Instrument AMC7834 via SPI

**URL:** <https://forum.arduino.cc/t/arduino-uno-with-texas-instrument-amc7834-via-spi/1317150>\
**Category:** Product Design\
**Created:** [October 31, 2024, 1:43pm UTC](https://forum.arduino.cc/t/arduino-uno-with-texas-instrument-amc7834-via-spi/1317150 "2024-10-31T13:43:05Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![stem88](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/stem88/32/904972_2.png) [@stem88](https://forum.arduino.cc/u/stem88)\
**Post date:** [October 31, 2024, 1:43pm UTC](https://forum.arduino.cc/t/arduino-uno-with-texas-instrument-amc7834-via-spi/1317150/1 "2024-10-31T13:43:05Z")

</div>

Hi all, I am pretty newby in Arduino but for an RF project I would like to interface the Arduino Uno to the [https://www.ti.com/product/AMC7834](https://www.ti.com/product/AMC7834). I would like to start reading Device ID only but the fact that I have to read 24 bits (3 bytes) is confusing me. Here below the code, if someone can help.

```arduino
#include <SPI.h>

//pin 13 SCLK
//pin 12 MISO on Arduino side, SDO on TXS
//pin 11 MOSI on Arduino side, SDI on TXS

const int csPin = 10; // Pin di selezione dello slave (CS)

void setup() {

  Serial.begin(9600);
  
  pinMode(csPin, OUTPUT);
  digitalWrite(csPin, HIGH); // Deseleziona l'SPI slave

  SPI.begin();
  SPI.setClockDivider(SPI_CLOCK_DIV2); // Imposta la velocità SPI
  SPI.setDataMode(SPI_MODE0); // Imposta il modo di SPI
}

void loop() {

  byte devID = readdevID();
  Serial.print("Device ID: ");
  Serial.println(devID);

  delay(1000);
}

byte readdevID() {
  
  digitalWrite(csPin, LOW);

  // First byte is to read the register (0x80 per leggere)
  byte command = 0x80 | 0x04;
  SPI.transfer(command);

  // Leggi i dati (2 byte)
  byte msb = SPI.transfer(0x000); // Ottieni il byte più significativo
  byte lsb = SPI.transfer(0x000); // Ottieni il byte a meno significativo

  digitalWrite(csPin, HIGH);

  byte devID = msb | lsb;
  return devID;
}

```

---

<div class="post-metadata">

**Author:** ![aliarifat794](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@aliarifat794](https://forum.arduino.cc/u/aliarifat794)\
**Post date:** [October 31, 2024, 1:56pm UTC](https://forum.arduino.cc/t/arduino-uno-with-texas-instrument-amc7834-via-spi/1317150/2 "2024-10-31T13:56:40Z")

</div>

The `AMC7834` datasheet specifies that the device ID is a 24-bit register, meaning it consists of three bytes. Your code needs some modification in this regard:

```arduino
#include <SPI.h>

// Pin connections to the SPI interface
const int csPin = 10; // Chip Select (CS) pin

void setup() {
  Serial.begin(9600);
  
  pinMode(csPin, OUTPUT);
  digitalWrite(csPin, HIGH); // Deselect the SPI slave

  SPI.begin();
  SPI.setClockDivider(SPI_CLOCK_DIV2); // Set SPI speed
  SPI.setDataMode(SPI_MODE0); // Set SPI mode
}

void loop() {
  // Read and print the device ID
  uint32_t devID = readDeviceID();
  Serial.print("Device ID: 0x");
  Serial.println(devID, HEX); // Print in hexadecimal format
  delay(1000);
}

uint32_t readDeviceID() {
  digitalWrite(csPin, LOW); // Select the SPI slave

  // Send command to read the device ID register
  byte command = 0x80 | 0x04; // Assuming 0x04 is the correct register address
  SPI.transfer(command);

  // Read the three bytes from the device ID register
  byte msb = SPI.transfer(0x00); // Most significant byte
  byte mid = SPI.transfer(0x00); // Middle byte
  byte lsb = SPI.transfer(0x00); // Least significant byte

  digitalWrite(csPin, HIGH); // Deselect the SPI slave

  // Combine the three bytes into a single 24-bit value
  uint32_t devID = ((uint32_t)msb << 16) | ((uint32_t)mid << 8) | lsb;
  return devID;
}

```

---

<div class="post-metadata">

**Author:** ![jim-p](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/jim-p/32/922840_2.png) [@jim-p](https://forum.arduino.cc/u/jim-p)\
**Post date:** [October 31, 2024, 2:13pm UTC](https://forum.arduino.cc/t/arduino-uno-with-texas-instrument-amc7834-via-spi/1317150/3 "2024-10-31T14:13:04Z")

</div>

@stem88

Your main problem is incompatible logic levels. The 7834 I/O are 3.3V and the Uno is 5V.  
So first thing is to buy a level translator.

> read 24 bits (3 bytes)

No, the ID is only 16 bits. **All** registers are only 16 bits (2 bytes)

Don't use setClockDiviseo or setDataMode  
Use instead

```arduino
SPI.beginTransaction(SPISettings(2000000, MSBFIRST, SPI_MODE0))

```

[https://docs.arduino.cc/language-reference/en/functions/communication/SPI/SPISettings/](https://docs.arduino.cc/language-reference/en/functions/communication/SPI/SPISettings/)

Also add a 10us delay after you bring CS low and before you bring it high

---

<div class="post-metadata">

**Author:** ![EmilyJane](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/emilyjane/32/821537_2.png) [@EmilyJane](https://forum.arduino.cc/u/EmilyJane)\
**Post date:** [October 31, 2024, 2:41pm UTC](https://forum.arduino.cc/t/arduino-uno-with-texas-instrument-amc7834-via-spi/1317150/4 "2024-10-31T14:41:51Z")

</div>

> [@aliarifat794](#):
>
> `AMC7834` datasheet specifies that the device ID is a 24-bit register

You are misinterpreting. Transfers are 24 bits composed of an 8-bit register address and a 16-bit register value.

---

<div class="post-metadata">

**Author:** ![system](https://dub1.discourse-cdn.com/arduino/user_avatar/forum.arduino.cc/system/32/1140315_2.png) [@system](https://forum.arduino.cc/u/system)\
**Post date:** [April 29, 2025, 2:42pm UTC](https://forum.arduino.cc/t/arduino-uno-with-texas-instrument-amc7834-via-spi/1317150/5 "2025-04-29T14:42:25Z")

</div>

Closed on April 29, 2025, 2:42pm UTC

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.