void config_cam_buffer()
{
    // init DMA
    DMA_CAM_RD_CH = dma_claim_unused_channel(true);
    mp_printf(MP_PYTHON_PRINTER, "DMA_CH= %d\n", (int)DMA_CAM_RD_CH);
    
    // Disable IRQ
    irq_set_enabled(DMA_IRQ_0, false);
    mp_printf(MP_PYTHON_PRINTER, "irq_set_enabled\n");

     // Configure DMA Channel 0
    dma_channel_config c0 = get_cam_config(pio_cam, sm_cam, DMA_CAM_RD_CH);
    mp_printf(MP_PYTHON_PRINTER, "dma_channel_config c0= %d\n", (int)&c0);
    
    channel_config_set_transfer_data_size(&c0, DMA_SIZE_16);
    mp_printf(MP_PYTHON_PRINTER, "channel_config_set_transfer_data_size\n");
    
    dma_channel_configure(DMA_CAM_RD_CH, &c0,
                          cam_ptr,               // Destination pointer
                          &pio_cam->rxf[sm_cam], // Source pointer
                          CAM_FUL_SIZE,          // Number of transfers
                          false                  // Don't Start yet
    );
    mp_printf(MP_PYTHON_PRINTER, "dma_channel_configure cam_ptr: %d\n", (int)cam_ptr);
    
    // IRQ settings
    dma_channel_set_irq0_enabled(DMA_CAM_RD_CH, true);
    mp_printf(MP_PYTHON_PRINTER, "dma_channel_set_irq0_enabled:\n");
    
    //irq_set_exclusive_handler(DMA_IRQ_0, cam_handler); // <-- FAILS HERE
    mp_printf(MP_PYTHON_PRINTER, "//irq_set_exclusive_handler: cam_handler\n");
    
    // irq_set_enabled(DMA_IRQ_0, true);
    // dma_channel_start(DMA_CAM_RD_CH); // Start DMA transfer
}