src/hal/boards/tx-bridge/txamp.c

 /**
- * Copyright 2016-2018
+ * Copyright 2016-2023
  * 
  * Bernd-Christian Renner, and
  * Hamburg University of Technology (TUHH).
@@ -37,7 +37,7 @@
 #include "hal_txamp.h"
 #include "txamp.h"
 #include "hal_gpio.h"
-#include "dev_mcp4561.h"
+#include "dev_mcp4551.h"
 
 
 #pragma message "building BRIDGE TX AMP"
@@ -148,9 +148,9 @@ txamp_disable()
 void
 txamp_connectOutput()
 {
-    // use non-volatile write here here
-    mcp4561_send(POTI_CMD_WRITE_DATA, TXGAIN[txLvl]);
-  
+    // use volatile write here to prevent memory corruption of poti
+    mcp4551_send(MCP4551_CMD_WRITE_DATA, TXGAIN[txLvl]);
+
     // only enable output, after gain has been set
     gpio_set(TXRX_SW_PIN);
 }

src/hal/dev/dev_mcp4561.h → src/hal/dev/dev_mcp4551.h

 /**
- * Copyright 2016-2018
+ * Copyright 2016-2023
  * 
  * Timo Kortbrae,
  * Bernd-Christian Renner, and
@@ -35,30 +35,30 @@
  */
 
 
-#ifndef DEV_MCP4561
-#define DEV_MCP4561
+#ifndef DEV_MCP4551
+#define DEV_MCP4551
 
 #include "mcu_i2c.h"
 
-#define MCP4561_ADDR  ((uint8_t)0x2E)   //!< I2C slave address of the digital potentiometer (mcp4561), 0101 prefix, A2 = A1 = 1 (pull-up), A0 as on PCB (0), Tbl. 6-2
+#define MCP4551_ADDR  ((uint8_t)0x2E)   //!< I2C slave address of the digital potentiometer (mcp4551), 0101 prefix, A2 = A1 = 1 (pull-up), A0 as on PCB (0), Tbl. 6-2 in data sheet
 
 /**
- *  \defgroup mcp4561_commands Commands for the digital potentiometer (mcp4561)
+ *  \defgroup mcp4551_commands Commands for the digital potentiometer (mcp4551)
  * @{
  */
-/// commands for the potentiometer (mcp4561)
+/// commands for the potentiometer (mcp4551)
 enum {
-    POTI_CMD_WRITE_DATA  = 0x00
+    MCP4551_CMD_WRITE_DATA  = 0x00
 };
 /** @} */
 
 /**
-  * @brief  initialisation of mcp4561 - nothing to do at the moment
+  * @brief  initialisation of mcp4551 - nothing to do at the moment
   *
   * @retval true if the initialisation was successful
   */
 static inline bool
-mcp4561_init(void)
+mcp4551_init(void)
 {
     return true;
 }
@@ -66,9 +66,9 @@ mcp4561_init(void)
 
 
 /**
-  * @brief  send a command to the digital potentiometer (mcp4561)
+  * @brief  send a command to the digital potentiometer (mcp4551)
   *
-  * @param cmd: command to be send - has to be one of the commands listed @link mcp4561_commands here@endlink
+  * @param cmd: command to be send - has to be one of the commands listed @link mcp4551_commands here@endlink
   * @param data: data to be send
   *
   * @retval true if the i2c transmission was started successfully
@@ -77,17 +77,21 @@ mcp4561_init(void)
 __attribute__((__always_inline__))
 #endif
 static inline bool
-mcp4561_send(uint8_t cmd, uint16_t data)
+mcp4551_send(uint8_t cmd, uint16_t data)
 {
     if (data > 256) {
         return false;
     }
     
-    // max value is 256, which is in second byte
+    // see MCP455X i2c data sheet, Sect 7.4 (page 54pp)
+    // max value is 256 with bit D8 in command byte
+    // CMD6:0,D8 | D7:0
+    // - 7 command bits including device memory address
+    // - 9 data bits spread
     uint8_t temp[2];
     temp[0] = cmd | (uint8_t)((data >> 8) & 0x01);
     temp[1] = (uint8_t)(data & 0xFF);
-    return i2c_transmitDMA(MCP4561_ADDR, temp, 2);
+    return i2c_transmitDMA(MCP4551_ADDR, temp, 2);
 }