---
title: "stm32f103xx spi + w5500 - Write successful but read returns 0"
url: "https://maker.wiznet.io/forum/13048"
markdown_url: "https://maker.wiznet.io/forum/13048/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "sr2018"
created: "2018-09-05T04:03:08+09:00"
last_activity: "2018-09-05T10:24:59+09:00"
language: "en"
views: 1054
replies: 3
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# stm32f103xx spi + w5500 - Write successful but read returns 0

## Question

Asked by sr2018 on 2018-09-05 in Ethernet Chips.

Hi There,
I am trying to get W5500 work as a TCP Server.
As initial steps, I first provided a static IP address so that I could test the spi connectivity between stm32f103xx microcontroller and w5500.
I have successfully programmed an IP address, Subnet mask, MAC Address and gateway address by using the VDM mode and writing to Common Register 0x0001-0x0012.
I pinged the w5500 and got a response and also did an arp -a to check the programmed MAC address.
both ping and arp were successful.

So far all is good. I have the following issues:
Issue 1:
Next I tried to read the programmed MAC address that I was able to see using the arp command.

I did the following

- Sent address High = 0x00, address Low = 0x09 and control = 0x00.
  The SPI mode is 0 and the host configured as the Master.
  I have activated SPI interrupt. So in the ISR I am checking" if((SPI1->SR & SPI_SR_RXNE) == SPI_SR_RXNE)" for any received data packets.
  I was expecting to receive the MAC Address but received 0x00 zeros.
  Next I tried reading the Version so wrote address High = 0x00, address Low = 0x39 and control = 0x00, but again received Zeros.

Note: All my write are successful and I receive a 0x01,0x02,0x03.

Issue 2:
Each time I open socket 0 by writing to Sn_Cr register, I cannot even ping the W5500.

I am using 3.3V, Port A PA4,5,6,7 for SPI1 on stm32f103xx.
I have connected the interrupt pin of W5500 to PB15.
Both port A and port B of stm32f103xx are activated in RCC, AFIO for SPI1 is activated.

Any help would be appreciated.
Thanks in advance.

## Replies

### Reply 1 by Eugeny, 2018-09-05

![](https://avatars.discourse-cdn.com/v4/letter/s/f04885/48.png) sr2018:

> but received 0x00 zeros
> …
> and I receive a 0x01,0x02,0x03

You must receive 0x01,0x02,0x03 also during read. If you do not, then it means W5500 does not recognize the command.

![](https://avatars.discourse-cdn.com/v4/letter/s/f04885/48.png) sr2018:

> Each time I open socket 0 by writing to Sn_Cr register, I cannot even ping the W5500.

Sounds like you write to wrong register page (e.g. to common register block).

### Reply 2 by sr2018, 2018-09-05 (in reply to reply 1)

Dear Eugeny,
Thanks for your prompt response.
I am for some reason not getting 0x01,0x02,0x03 for read.
To read the version number, I am transmitting the following:

1. Address High Byte = 0x00, Low Byte = 0x39

2. BSB,RWB,OM = 0x00

3. I keep the Chip select line low so that I can sequentially receive data but I only receive a couple of 0x00s.

For the second problem regarding Socket 0:
I am doing the following to open TCP socket and then listen to it:

1. To Select TCP - Address High Byte = 0x00, Address Low Byte = 0x00, BSB,RWB,OM (VDM) = 0x0C and data = 0x21 (To enable ND/NC/MMB and TCP)

2. I specify port number as 9000 (in hex 0x23,0x28), I write the following to the W5500 - Address High Byte = 0x00, Address Low Byte = 0x04, BSB,RWB,OM (VDM) = 0x0C and data = 0x23, 0x28

3. I enable the socket interrupt - Address High Byte = 0x00, Address Low Byte = 0x2C, BSB,RWB,OM (VDM) = 0x0C and data = 0x1F

4. I set RX Buf size as Address High Byte = 0x00, Address Low Byte = 0x1E, BSB,RWB,OM (VDM) = 0x0C and data = 0x02 (2Kb)

5. I set TX Buf size as Address High Byte = 0x00, Address Low Byte = 0x1F, BSB,RWB,OM (VDM) = 0x0C and data = 0x02 (2Kb)

6. Socket OPEN - Address High Byte = 0x00, Address Low Byte = 0x01, BSB,RWB,OM (VDM) = 0x0C and data = 0x01

7. Socket Listen - Address High Byte = 0x00, Address Low Byte = 0x01, BSB,RWB,OM (VDM) = 0x0C and data = 0x02
   Socket open and listen are in the CR register 0x00, 0x01.

When I write I immediately pull the CS line up after the last byte is written and I receive 0x01,0x02,0x03.
However for read I let the CS line low so that I can read sequentially but do not receive any valid data, only Zeros.

Am I missing something?
Your help would be most appreciated.
Thanks,
SR

### Reply 3 by Eugeny, 2018-09-05

Please share scope shot of the communication between MCU and W5500 (in the best case having all 4 waveforms altogeter) for reads and writes.

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Source: https://maker.wiznet.io/forum/13048