#define MAX_MSG_LEN 16   // may be increased if necessary to max 251

static const hm2_modbus_chan_descriptor_t channels = {
/*  {TYPE,    FUNC, ADDR,   COUNT, pin_name} */
    {HAL_U32, 3,  0x0611, 1,     "error_code"},
    {HAL_U32, 3,  0x2101, 1,     "status"},
    {HAL_FLOAT, 3,  0x2104, 1,     "output-current"},
    {HAL_FLOAT, 3,  0x2105, 1,     "bus-voltage"},  
    {HAL_FLOAT, 3,  0x210C, 1,     "motor-speed"},
    {HAL_FLOAT, 6,  0x2001, 1,     "frequency-command"},
    {HAL_U32, 6,  0x2000, 1,     "operation"},
};