ST SPWF04S Series, User Manual

Page: 8 / 66

4 SPI protocol
By setting to 0 the configuration variable "console_enabled", the module is enabled to use the SPI interface in
place of the UART.
The data transferred over the MISO and MOSI signals are packed using a well-defined API packet format as
represented below.
Figure 4. SPI packet formats
Table 2. KindOfEvent Byte SubField
Bits Event type
Bits 0:3
Status variable wifi_state values range. Refer to
Table 8. Status variables .
Bits 4:7
Allowed values are:
•
0x01 for common indications like WIND or action
confirmations
• 0x02 for critical error notifications
• 0x03 for incoming data sent over the SPI (in this case
normally data are filled into payload field)
Table 3. Indication number field
Event type Bits 4:7 Indication number
0x01 Refer to Table 14. WIND messages .
0x02
Refer to Table 10. AT-S.ERROR:=ERROR ID= =ERROR
String= .
0x03 Data payload.
Commands over the SPI have a max length of 512 bytes.
To map an AT command in the equivalent SPI command, the following procedure applies:
1.
Use the corresponding CMD ID specified in Table 1. SPWF04Sx commands and fill the 4
th
bytes of the
master packet.
2. If optional parameters are available, count the number of comma-separated items after the “=” character and
with that number the 6
th
byte of the message. Starting from the 7
th
byte, start to write 1 byte containing the
field lengths and then copy the field bytes. Then continue with the remaining parameters.
UM2114
SPI protocol
UM2114 - Rev 3
page 8/66