1 files changed, 113 insertions, 0 deletions

diff --git a/firmware/target/arm/s5l8700/ipodnano2g/serial-nano2g.c b/firmware/target/arm/s5l8700/ipodnano2g/serial-nano2g.c
index 487984fbe3..5ff0b0ca25 100644
--- a/firmware/target/arm/s5l8700/ipodnano2g/serial-nano2g.c
+++ b/firmware/target/arm/s5l8700/ipodnano2g/serial-nano2g.c
@@ -47,6 +47,9 @@
 
 
 extern const struct uartc s5l8701_uartc0;
+#ifdef IPOD_ACCESSORY_PROTOCOL
+void iap_rx_isr(int, char*, char*, uint32_t);
+#endif
 
 struct uartc_port ser_port IDATA_ATTR =
 {
@@ -61,7 +64,11 @@ struct uartc_port ser_port IDATA_ATTR =
     .clkhz = NANO2G_UART_CLK_HZ,
 
     /* interrupt callbacks */
+#ifdef IPOD_ACCESSORY_PROTOCOL
+    .rx_cb = iap_rx_isr,
+#else
     .rx_cb = NULL,
+#endif
     .tx_cb = NULL,  /* polling */
 };
 
@@ -94,3 +101,109 @@ void tx_writec(unsigned char c)
 {
     uartc_port_tx_byte(&ser_port, c);
 }
+
+
+#ifdef IPOD_ACCESSORY_PROTOCOL
+#include "iap.h"
+
+static enum {
+    ABR_STATUS_LAUNCHED,    /* ST_SYNC */
+    ABR_STATUS_SYNCING,     /* ST_SOF */
+    ABR_STATUS_DONE
+} abr_status;
+
+void serial_bitrate(int rate)
+{
+    logf("[%lu] serial_bitrate(%d)", (uint32_t)USEC_TIMER, rate);
+
+    if (rate == 0) {
+        /* Using auto-bitrate (ABR) to detect accessory Tx speed:
+         *
+         * + Here:
+         *   - Disable Rx logic to clean the FIFO and the shift
+         *     register, thus no Rx data interrupts are generated.
+         *   - Launch ABR and wait for a low pulse in Rx line.
+         *
+         * + In ISR, when a low pulse is detected (ideally it is the
+         *   start bit of 0xff):
+         *   - Calculate and configure detected speed.
+         *   - Enable Rx to verify that the next received data frame
+         *     is 0x55 or 0xff:
+         *     - If so, it's assumed bit rate is correctly detected,
+         *       it will not be modified until speed is changed using
+         *       RB options menu.
+         *     - If not, reset iAP state machine and launch a new ABR.
+         */
+        uartc_port_set_rx_mode(&ser_port, UCON_MODE_DISABLED);
+        uartc_port_abr_start(&ser_port);
+        abr_status = ABR_STATUS_LAUNCHED;
+    }
+    else {
+        uint32_t brdata;
+        if      (rate == 57600) brdata = BRDATA_57600;
+        else if (rate == 38400) brdata = BRDATA_38400;
+        else if (rate == 19200) brdata = BRDATA_19200;
+        else brdata = BRDATA_9600;
+        uartc_port_abr_stop(&ser_port); /* abort ABR if already launched */
+        uartc_port_set_bitrate_raw(&ser_port, brdata);
+        uartc_port_set_rx_mode(&ser_port, UCON_MODE_INTREQ);
+        abr_status = ABR_STATUS_DONE;
+    }
+}
+
+void iap_rx_isr(int len, char *data, char *err, uint32_t abr_cnt)
+{
+    /* ignore Rx errors, upper layer will discard bad packets */
+    (void) err;
+
+    static int sync_retry;
+
+    if (abr_status == ABR_STATUS_LAUNCHED) {
+        /* autobauding */
+        if (abr_cnt) {
+            #define BR2CNT(s) (NANO2G_UART_CLK_HZ / (unsigned)(s))
+            if (abr_cnt < BR2CNT(57600*1.1) || abr_cnt > BR2CNT(9600*0.9)) {
+                /* detected speed out of range, relaunch ABR */
+                uartc_port_abr_start(&ser_port);
+                return;
+            }
+            /* valid speed detected, select it */
+            uint32_t brdata;
+            if      (abr_cnt < BR2CNT(48000)) brdata = BRDATA_57600;
+            else if (abr_cnt < BR2CNT(33600)) brdata = BRDATA_38400;
+            else if (abr_cnt < BR2CNT(24000)) brdata = BRDATA_28800;
+            else if (abr_cnt < BR2CNT(14400)) brdata = BRDATA_19200;
+            else brdata = BRDATA_9600;
+
+            /* set detected speed */
+            uartc_port_set_bitrate_raw(&ser_port, brdata);
+            uartc_port_set_rx_mode(&ser_port, UCON_MODE_INTREQ);
+
+            /* enter SOF state */
+            iap_getc(0xff);
+
+            abr_status = ABR_STATUS_SYNCING;
+            sync_retry = 2; /* we are expecting [0xff] 0x55 */
+        }
+    }
+
+    /* process received data */
+    while (len--)
+    {
+        bool sync_done = !iap_getc(*data++);
+
+        if (abr_status == ABR_STATUS_SYNCING)
+        {
+            if (sync_done) {
+                abr_status = ABR_STATUS_DONE;
+            }
+            else if (--sync_retry == 0) {
+                /* invalid speed detected, relaunch ABR
+                   discarding remaining data (if any) */
+                serial_bitrate(0);
+                break;
+            }
+        }
+    }
+}
+#endif /* IPOD_ACCESSORY_PROTOCOL */