diff options
Diffstat (limited to 'examples/io/pads/spi.c')
| -rw-r--r-- | examples/io/pads/spi.c | 22 |
1 files changed, 12 insertions, 10 deletions
diff --git a/examples/io/pads/spi.c b/examples/io/pads/spi.c index 4728626..5fc2648 100644 --- a/examples/io/pads/spi.c +++ b/examples/io/pads/spi.c @@ -2,9 +2,9 @@ * PSn00bSDK controller polling example (SPI driver) * (C) 2021 spicyjpeg - MPL licensed * - * This is a fairly complete timer driven high-speed SPI driver, with support - * for sending custom commands (including memory card reads/writes), in about - * 200 lines of code. Feel free to copypaste and adapt it. + * This is a fairly complete timer driven, asynchronous high-speed SPI driver, + * with support for sending custom commands (including memory card access), in + * about 200 lines of code. Feel free to copypaste and adapt it. * * The way this works is by maintaining a queue of requests to send, each with * its own payload and callback. Timer 2 is configured to trigger an IRQ at @@ -42,8 +42,12 @@ #define TIM_VALUE(N) *((volatile uint32_t *) 0x1f801100 + 4 * (N)) #define TIM_CTRL(N) *((volatile uint32_t *) 0x1f801104 + 4 * (N)) #define TIM_RELOAD(N) *((volatile uint32_t *) 0x1f801108 + 4 * (N)) -#define JOY_TXRX *((volatile uint32_t *) 0x1f801040) -#define JOY_STAT *((volatile uint32_t *) 0x1f801044) + +// IMPORTANT: even though JOY_TXRX is a 32-bit register, it should only be +// accessed as 8-bit. Reading it as 16 or 32-bit works fine on real hardware, +// but leads to problems in some emulators. +#define JOY_TXRX *((volatile uint8_t *) 0x1f801040) +#define JOY_STAT *((volatile uint16_t *) 0x1f801044) #define JOY_MODE *((volatile uint16_t *) 0x1f801048) #define JOY_CTRL *((volatile uint16_t *) 0x1f80104a) #define JOY_BAUD *((volatile uint16_t *) 0x1f80104e) @@ -142,11 +146,9 @@ static void spi_ack_handler(void) { if (!ctx.rx_len) { // We just sent the first address byte. Obviously the response we // received was read from an open bus, so the SPI port's internal FIFO - // must be flushed to ensure we are only going to read valid data from - // now on. - volatile uint32_t dummy; - while (JOY_STAT & 0x0002) - dummy = JOY_TXRX; + // must be flushed (by performing dummy reads) to ensure we are only + // going to read valid data from now on. + JOY_TXRX; } else if (ctx.rx_len <= SPI_BUFF_LEN) { // If this is not the first byte, put it in the RX buffer. |