crewID/libnfc
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

spi: fix doc typos

Browse source
This commit is contained in:
Philippe Teuwen 2013-03-27 22:58:59 +01:00
parent 12b756e97a
commit 7df8fdd0f6
2 changed files with 5 additions and 5 deletions
Download patch file Download diff file Expand all files Collapse all files

8
libnfc/drivers/pn532_spi.c
View file

@ -363,7 +363,7 @@ pn532_spi_receive_next_chunk(nfc_device *pnd, uint8_t *pbtData, const size_t szD
{
// According to datasheet, the entire read operation should be done at once
// However, it seems impossible to do since the length of the frame is stored in the frame
// itself and it's impossible to manualy set CS to low between two read operations
// itself and it's impossible to manually set CS to low between two read operations
// It's possible to read the response frame in a series of read operations, provided
// each read operation is preceded by SPI_DATAREAD byte from the host.
@ -374,16 +374,16 @@ pn532_spi_receive_next_chunk(nfc_device *pnd, uint8_t *pbtData, const size_t szD
// Many hardware SPI implementations are half-duplex, so it's became impossible to read this
// first response byte
// The following hack is used here: we first try to recieve data from PN532 without SPI_DATAREAD
// The following hack is used here: we first try to receive data from PN532 without SPI_DATAREAD
// and then begin full-featured read operation
// The PN532 do not shift the internal register on the recieve operation, which allows us to read the whole response
// The PN532 does not shift the internal register on the receive operation, which allows us to read the whole response
// The example transfer log is as follows:
// CS ..._/---\___________________________/---\________/------\_____________/-----\_________/---\____________/---...
// MOSI (host=>pn532) ... 0x03 0x00 0x00 0x00 0x00 0x00 0x03 0x00 0x00 0x03 0x00
// MISO (pn532<=host) ... 0x01 0x00 0xff 0x02 0xfe 0xd5 0xd5 0x15 0x16 0x16 0x00
// linux send/recieve s r r r r r s r r s r
// linux send/receive s r r r r r s r r s r
// |<-- data -->| |<-data->| |<-data->| |<-data->| |<-data->|
// |<-- first chunk -->| |<-- second chunk -->| |<-- third chunk -->|