---
title: "emac_w5500_transmit(473): free size(42) send length (4)"
url: "https://maker.wiznet.io/forum/15136"
markdown_url: "https://maker.wiznet.io/forum/15136/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "WAVEWT"
created: "2024-01-30T01:45:11+09:00"
last_activity: "2024-01-30T01:45:11+09:00"
language: "en"
views: 108
replies: 0
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# emac_w5500_transmit(473): free size(42) send length (4)

## Question

Asked by WAVEWT on 2024-01-30 in Ethernet Chips.

I’m using ESP32s3(ESP-IDF v5.1) and implementing Modbus RTU with W5500.

After the code initialized W5500 and Modbus RTU,
I can see this error randomly even code does not start Modbus RTU

emac_w5500_transmit(473): free size (42) < send length (4)

I do not know why ESP32s3 shows this error.

How can I remove this error?

---

Source: https://maker.wiznet.io/forum/15136