ESP8266 SPI Driver
Some general information about the SPI hardware and my investigations into the control registers are on http://d.av.id.au/blog/ for those who want a deeper insight into how the code works.
HSPI Hardware Pins
| Pin Name | GPIO # | HSPI Function |
|---|---|---|
| MTDI | GPIO12 | MISO (DIN) |
| MTCK | GPIO13 | MOSI (DOUT) |
| MTMS | GPIO14 | CLOCK |
| MTDO | GPIO15 | CS / SS |
Main SPI Transaction Function
Perform an SPI transaction.
spi_transaction(spi_no, cmd_bits, cmd_data, addr_bits, addr_data, dout_bits, dout_data, din_bits, dummy_bits)
spi_no: SPI or HSPI
cmd_bits: length of command. Set to 0 to disable command component.
cmd_data: Command data to send.
addr_bits: length of address. Set to 0 to disable address component.
addr_data: Address data to send.
dout_bits: Length of data payload to send. Set to 0 to disable data out component.
dout_data: Data payload to send.
din_bits: Length of data payload to receive. Set to 0 if not receiving any data.
dummy_bits: Number of dummy bits to insert.
Data Structure of SPI Transaction
[COMMAND]+[ADDRESS]+[DataOUT]+[DUMMYBITS]+[DataIN]
If no data is set to be received, then the Dummy bits are inserted before DataOUT.
[COMMAND]+[ADDRESS]+[DUMMYBITS]+[DataOUT]
Example:
Writing data to EEPROM
Command = 0b101 (3 bit write command)
Address = 0b111110011 or 0x1F3 (9 bit data address)
Data = 0b11001100 or 0xCC (8 bits of data)
SPI Transaction Packet = 0b10111111001111001100 or 0xBF3CC
spi_transaction(HSPI, 3, 0b101, 9, 0x1F3, 8, 0xCC, 0, 0);
Reading data from EEPROM
Command = 0b110 (3 bit read command)
Address = 0b111110011 or 0x1F3 (9 bit data address)
(8 bits of data to read)
SPI Transaction Packet = 0b11011111001100000000 or 0xDF300 //last 8 zeros are to clock 8 bits from the EEPROM
data_read = (uint8) spi_transaction(HSPI, 3, 0b101, 9, 0x1F3, 0, 0, 8, 0);
Basic Transmit Functions
Send 'n' bits of data: spi_txd(spi_no, bits, data)
Send 8 bits of data (1 BYTE): spi_tx8(spi_no, data)
Send 16 bits of data (1 WORD): spi_tx16(spi_no, data)
Send 32 bits of data (1 DWORD): spi_tx32(spi_no, data)
Example:
uint8 byte = 0xEF;
uint16 word = 0xBEEF;
uint32 dword = 0xDEADBEEF;
uint16 9bit = 0b101010101;
spi_tx8(HSPI, byte);
spi_tx16(HSPI, word);
spi_tx32(HSPI, dword);
spi_txd(HSPI, 9, 9bit);
Basic Receive Functions
Receive 'n' bits of data: spi_rxd(spi_no, bits)
Receive 8 bits of data (1 BYTE): spi_rx8(spi_no)
Receive 16 bits of data (1 WORD): spi_rx16(spi_no)
Receive 32 bits of data (1 DWORD): spi_rx32(spi_no)
Example:
uint8 byte;
uint16 word;
uint32 dword;
uint16 9bit;
byte = (uint8) spi_rx8(HSPI); //returned value is uint32. Cast to uint8
word = (uint16) spi_rx16(HSPI); //returned value is uint32. Cast to uint16
dword = spi_rx32(HSPI); //No type casting needed
9bit = (uint16) spi_rxd(HSPI, 9); //returned value is uint32. Cast to uint16